I found starting a new bot with Net 6.0 and then pasting in the code from the old bot that was on 4.x worked. I would then delete the old bot and rename the new bot with the old label.
The error was a concern as I had open trades using the label name and changing back to 4.x did not resolve the error. Creating a new bot was the solution.
I have left most bots with 4.x and now have others working on Net 6.0
