.NET fails to save Word as PDF from Scheduled Task on WIN-16 server - The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)

I have a .NET application I moved to Win-16 server. The save Word document as PDF among other things. Every time I run it manually by double-clicking the exe file it works without any issues however when I run it from scheduled task in Task Scheduler I am getting this error when saving the Word as PDF: The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)

For days we've tried to get it to work from the scheduled task and it worked a couple of times but then again it stopped working.

It is something specific to the Task Scheduler on the 2016 server because every time I run it on that same server directly from exe it connects without any issues.

Can someone please help?