Hi jungledede,
TestStand is still in the process of migrating completely to .NET Core. The .NET adapter (which is responsible for loading and executing your code module) is already fully in .NET 8.
The Sequence Editor, built-in step types and tools etc which are also .NET based are not migrated yet and this is being worked on for the next TestStand release. Once done, all these applications will be in .NET 8 as well. Currently they are still in .NET framework 4.8.
You should be able to target your code modules to .NET 8 and use them with TestStand 2024 Q4, that is the expected workflow.
From the fact that you are able to execute your dll through a .NET 8 executable without issues and that the exception is not a FileNotFound but rather InvalidOperation, i would suspect that the issue might not be related to having dependencies in the GAC.
Would you be able to provide a simplified version of your code which shows the error so we can check what's going on. Just based on looking at your code snapshot, i am unsure why an InvalidOperation exception is being thrown.
Regards,
Tinu