I tried both the download from DEVSENSE and the Visual Studio Extension Store. Both give the same error and wont complete installation. Installed both with admin access. Installer Log below:
10/26/2020 08:22:32 - The extension with ID '97D92282-92CB-492E-AA3E-B9506D2C0740' is not installed to Visual Studio Community 2019.
10/26/2020 08:22:32 - Initializing Install...
10/26/2020 08:22:32 - Extension Details...
10/26/2020 08:22:32 - 	Identifier         : 97D92282-92CB-492E-AA3E-B9506D2C0740
10/26/2020 08:22:32 - 	Name               : PHP Tools for Visual Studio 2019
10/26/2020 08:22:32 - 	Author             : DEVSENSE
10/26/2020 08:22:32 - 	Version            : 1.40.12178
10/26/2020 08:22:32 - 	Description        : Provides full featured support for editing and debugging PHP programs.
10/26/2020 08:22:32 - 	Locale             : en-US
10/26/2020 08:22:32 - 	MoreInfoURL        : http://www.devsense.com/
10/26/2020 08:22:32 - 	InstalledByMSI     : False
10/26/2020 08:22:32 - 	SupportedFrameworkVersionRange : [4.6]
10/26/2020 08:22:32 - 
10/26/2020 08:22:33 - 	SignatureState     : InvalidCertificate
10/26/2020 08:22:33 - 	SignedBy           : DEVSENSE s.r.o.
10/26/2020 08:22:33 - 	Certificate Info   : 
10/26/2020 08:22:33 - 		-------------------------------------------------------
10/26/2020 08:22:33 - 		[Subject]       : CN=DEVSENSE s.r.o., O=DEVSENSE s.r.o., STREET=Zemedelska 1579/16, L=Prague, S=Prague, PostalCode=16000, C=CZ
10/26/2020 08:22:33 - 		[Issuer]        : CN=Sectigo RSA Code Signing CA, O=Sectigo Limited, L=Salford, S=Greater Manchester, C=GB
10/26/2020 08:22:33 - 		[Serial Number] : 00C7D01204AB5E1D8BBE02C93F898E38A0
10/26/2020 08:22:33 - 		[Not Before]    : 4/13/2020 17:00:00
10/26/2020 08:22:33 - 		[Not After]     : 4/14/2023 16:59:59
10/26/2020 08:22:33 - 		[Thumbprint]    : 585ECF995363594DE2A6F8216813875BDAF5AF8C
10/26/2020 08:23:49 - Beginning to install extension to Visual Studio Community 2019...
10/26/2020 08:23:50 - Failed to create scheduled task: UpdateConfiguration_S-1-5-82-2620321712-1700930904-940408522-4289904328-3628634125
10/26/2020 08:23:50 - Failed to create the update configuration task for user IIS APPPOOL\SchToolDBv4-DEV: (9,80):UserId:S-1-5-82-2620321712-1700930904-940408522-4289904328-3628634125
10/26/2020 08:23:50 - Failed to create scheduled task: UpdateConfiguration_S-1-5-82-3642516838-1749693018-1272362595-906508932-4129025788
10/26/2020 08:23:50 - Failed to create the update configuration task for user IIS APPPOOL\ASP.NET V2.0 Integrated: (9,80):UserId:S-1-5-82-3642516838-1749693018-1272362595-906508932-4129025788
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.Windows.UniversalCRT.Msu.8: The current OS Version '10.0.19041.0' is not in the supported version range '[6.2,6.3)'.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.Windows.UniversalCRT.Msu.81: The current OS Version '10.0.19041.0' is not in the supported version range '[6.3,6.4)'.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.Net.4.7.2.FullRedist: The current OS Version '10.0.19041.0' is not in the supported version range '[6.1.1,10.0.16299]'.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.VisualStudio.Debugger.DbgHelp.Win8: The current OS Version '10.0.19041.0' is not in the supported version range '[6.1,6.3]'.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.VisualStudio.Debugger.Remote.DbgHelp.Win8: The current OS Version '10.0.19041.0' is not in the supported version range '[6.1,6.3]'.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.VisualStudio.Debugger.Remote.DbgHelp.Win8: The current OS Version '10.0.19041.0' is not in the supported version range '[6.1,6.3]'.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.VisualStudio.NuGet.PowershellBindingRedirect: The current OS Version '10.0.19041.0' is not in the supported version range '[6.1,6.2)'.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.Windows.UniversalCRT.Msu.7: The current OS Version '10.0.19041.0' is not in the supported version range '[6.1,6.2)'.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.DiagnosticsHub.KB2882822.Win7: The current OS Version '10.0.19041.0' is not in the supported version range '[6.1,6.2)'.
10/26/2020 08:23:52 - Windows Installer found the package 'msodbcsql,version=16.0.62008.3130,chip=x64,language=en-US' superseded but corresponding compatible package information was not found. Attempts to repair will be skipped and that to uninstall may leave the cache behind.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.Net.4.8.FullRedist: The current OS Version '10.0.19041.0' is not in the supported version range '[6.1.1,10.0.17763]'.
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.Azure.PowerShell: Required conditions are not satisfied: Not Powershell5
10/26/2020 08:23:52 - Skipping non-applicable package Microsoft.VisualStudio.OfficeDeveloperTools.WindowsIdentityFoundation.Msu: The current OS Version '10.0.19041.0' is not in the supported version range '(,6.2)'.
10/26/2020 08:23:56 - Certificate is invalid: PHP.VS.vsix
10/26/2020 08:23:56 - Cache failed. Retrying download of '97D92282-92CB-492E-AA3E-B9506D2C0740,version=1.40.12178'.
10/26/2020 08:23:56 - Value cannot be null.
Parameter name: uri
10/26/2020 08:23:56 - Value cannot be null.
Parameter name: uri
10/26/2020 08:23:56 - Activity threw exception System.ArgumentNullException: Value cannot be null.
Parameter name: uri
10/26/2020 08:23:56 - Skipping cache of package '97D92282-92CB-492E-AA3E-B9506D2C0740,version=1.40.12178' since installing or downloading it failed
10/26/2020 08:23:56 - Skipping cache of package 'Component.97D92282-92CB-492E-AA3E-B9506D2C0740,version=1.40.12178' since the package or a parent package had a vital failure.
10/26/2020 08:25:05 - Install Error : System.AggregateException: One or more errors occurred. ---> Microsoft.VisualStudio.Setup.PackageFailureException: Package '97D92282-92CB-492E-AA3E-B9506D2C0740' failed to download
   at Microsoft.VisualStudio.Setup.InstallOperation.Run(CancellationToken token)
   at Microsoft.VisualStudio.Setup.Engine.RunOperation(InstallOperation installOperation, CancellationToken token, ExecuteAction action, ITelemetryOperation telemetryOperation)
   at Microsoft.VisualStudio.Setup.Engine.RunCoreOperation(InstallOperation coreOperation, ExecuteAction action, ITelemetryOperation telemetryOperation, CancellationToken token)
   at Microsoft.VisualStudio.Setup.Engine.Install(Product product, String destination, CancellationToken token)
   at Microsoft.VisualStudio.ExtensionManager.SetupEngineService.<Install>b__14_0()
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
   at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
   at Microsoft.VisualStudio.ExtensionManager.SetupEngineService.Install()
   at Microsoft.VisualStudio.ExtensionManager.ExtensionEngineImpl.PerformSetupEngineInstall(InstallableExtensionImpl extension, Boolean installPerMachine, Boolean isPackComponent, IDictionary`2 extensionsInstalledSoFar, List`1 extensionsUninstalledSoFar, IInstalledExtensionList modifiedInstalledExtensionsList, IProgress`1 progress, InstallFlags installFlags, AsyncOperation asyncOp, Version targetedVsVersion, IInstalledExtension& newExtension)
   at Microsoft.VisualStudio.ExtensionManager.ExtensionEngineImpl.InstallInternal(InstallableExtensionImpl extension, InstallFlags installFlags, IDictionary`2 extensionsInstalledSoFar, List`1 extensionsUninstalledSoFar, IInstalledExtensionList modifiedInstalledExtensionsList, AsyncOperation asyncOp, IProgress`1 progress, Version targetedVsVersion)
   at Microsoft.VisualStudio.ExtensionManager.ExtensionEngineImpl.BeginInstall(IInstallableExtension installableExtension, InstallFlags installFlags, AsyncOperation asyncOp, Version targetedVsVersion)
   at Microsoft.VisualStudio.ExtensionManager.ExtensionEngineImpl.InstallWorker(IInstallableExtension extension, InstallFlags installFlags, AsyncOperation asyncOp)
---> (Inner Exception #0) Microsoft.VisualStudio.Setup.PackageFailureException: Package '97D92282-92CB-492E-AA3E-B9506D2C0740' failed to download
   at Microsoft.VisualStudio.Setup.InstallOperation.Run(CancellationToken token)
   at Microsoft.VisualStudio.Setup.Engine.RunOperation(InstallOperation installOperation, CancellationToken token, ExecuteAction action, ITelemetryOperation telemetryOperation)
   at Microsoft.VisualStudio.Setup.Engine.RunCoreOperation(InstallOperation coreOperation, ExecuteAction action, ITelemetryOperation telemetryOperation, CancellationToken token)
   at Microsoft.VisualStudio.Setup.Engine.Install(Product product, String destination, CancellationToken token)
   at Microsoft.VisualStudio.ExtensionManager.SetupEngineService.<Install>b__14_0()
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()<---