Parallel Processing Error

[ScottSpurgeon]

Running ArcGIS Pro version 3.3.0, advanced licensure

I recently ran into some issues with certain geoprocessing tools failing (error 999999) after a consistent amount of time (usually just over 3 minutes of runtime). After a lot of troubleshooting, including an update to 3.4.0, I still couldn't get the tools to work. 

I've since discovered that any tools that attempt to use parallel processing will try to initialize it (e.g. "distributing operation across X parallel instances") and then throw a 999999 error.  

Is there anything I can do to resolve this? I have quite a strong computing system and I'd like to be able to use parallel processing, but as of now I'm forced to enter "0" in the parallel processing factor field to turn it off to ensure the tool runs. The only hint that I have is that I updated my .NET Runtime recently, and I think it was before the errors began. Currently have .NET SDK 8.0.405 (x64) and Desktop versions 8.0.12 and 8.0.13

[Robert_LeClair]

There was an old BUG-000129060 - "Parallel processing causes the Copy Raster geoprocessing tool to fail" that was fixed at ArcGIS Pro 3.0 so that's not it.  But it say not to set anything in the Parallel Processing box (leave empty) as ArcGIS Pro determines the optimial parallel processing by default.

[ScottSpurgeon]

Right. When not specifying a value (e.g. a percentage) or not specifying a value (leaving empty) I get the same failure, and it happens with various tools if they try to initialize parallel processing. If I leave the field blank and the tool determines that parallel processing isn't needed, the tool works. 

[ScottSpurgeon]

Update - I am now running ArcGIS Pro version 3.4.3 and still getting the same tool failures.