And I've solved this, at least temporarily!
$ cd /Users/$USER/.vscode/extensions/devsense.phptools-vscode-1.0.4654/out/server
$ nano Devsense.PHP.LanguageServer
Now add this to the file and save.
#!/usr/bin/env bash
dotnet /Users/$USER/.vscode/extensions/devsense.phptools-vscode-1.0.4654/out/server/Devsense.PHP.LanguageServer.dll
Lastly, just in case:
$ chmod +x Devsense.PHP.LanguageServer
Reload, and it should work!