how to resolve The message filter indicated that the application is busy. (Exception from HRESULT: 0x8001010A (RPC_E_SERVERCALL_RETRYLATER))

I ended up removing:

 PowerPoint_App.Visible = MsoTriState.msoTrue;

And it worked...!!!

I'm working through a similar problem (controlling Excel via PowerShell), and wanted to add that -- in a way I cannot begin to explain -- the analogue to @Milind Anantwar's suggestion caused my script to start working.

More details, in case they help:

• In my case, everything worked fine when run locally. I started seeing the

  Application is busy

  exception only when I moved to executing via an Azure Hybrid Worker Runner.

• With reference to the following snippet, I was seeing the exception after line 2, but removing line 2 "fixed" the problem:

  $excel = New-Object -ComObject Excel.Application    
  $excel.visible = $SHOW_EXCEL    
  $workbook = $excel.Workbooks.Open($_excel_file) 
  

• I saw the exception when $SHOW_EXCEL was set to $false.