UPDATE:
I fixed it!
Cause of the error:
aaPanel uses its own internal version of Python, and aaPanel version 7 isn't compatible with the Python version of aaPanel version 6.
Fix:
Run this command: 
Note: This is to update to version 7. If by the time you're reading this the latest version is 8, change the 7 to 8 in the URL above.
What does the command do:
It tries to update to Version 7 again and will update the Python version as well.
This command is totally safe and will NOT break anything. It won't alter your websites or linux installation. It will simply update aaPanel to a newer version.