Hey MiloslavBeno,
I believe "C:\Program Files (x86)\IIS Express" is locked down and requires Admin permissions to make changes.
Here is an entry from the error log:
<entry>
<record>1070</record>
<time>2020/12/07 15:55:56.243</time>
<type>Error</type>
<source>Editor or Editor Extension</source>
<description>System.UnauthorizedAccessException: Access to the path 'C:\Program Files (x86)\IIS Express\PHP\v7.4\php.ini' is denied.
 at System.IO.Error.WinIOError(Int32 errorCode, String maybeFullPath)
 at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
 at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
 at System.IO.StreamReader..ctor(String path, Encoding encoding, Boolean detectEncodingFromByteOrderMarks, Int32 bufferSize, Boolean checkHost)
 at System.IO.StreamReader..ctor(String path)
 at Devsense.PHP.Nodes.Environments.Config.PHPIniFile.Parse()
 at Devsense.PHP.Config.IISExpress.IISConfigHelper.GetPHPConfigInfo()
 at Devsense.PHP.Nodes.Environments.IIS.IISServerConfiguration.GetPHPConfigInfo()
 at Devsense.PHP.Nodes.Environments.IIS.IISSiteConfiguration.<Validate>d15.MoveNext()
 at System.Linq.Enumerable.<ConcatIterator>d__591.MoveNext()
 at System.Linq.Enumerable.Any[TSource](IEnumerable
1 source, Func2 predicate)
 at Devsense.PHP.Nodes.Environments.IssuesNotificationControl.<>c__DisplayClass7_0.<Revalidate>b__0()
 at Devsense.VisualStudio.Shell.GuardedOperations.Call[T](Object source, Func
1 action, T default)
--- End of stack trace from previous location where exception was thrown ---
 at Microsoft.VisualStudio.Telemetry.WindowsErrorReporting.WatsonReport.GetClrWatsonExceptionInfo(Exception exceptionObject)</description>
</entry>
I tried switching the Server runtime to "PHP 7.3.13" instead of "PHP 7.4.1", but still same error. Also, it was still trying to access the php.ini file in the "7.4" directory. I found that odd.
Let me know what else you need to track this down.
Thanks.