Hi,
I am using ArcGIS 10.8.1 with a fresh install. I originally tried in 10.7.1. I am using the correct version of the districting extension for the ArcMap version I am using. I am able to create a plan but I can't reopen it or create another one. It tries to open with the following error.

If i try to open the mxd that is created for a plan. I get this error:

Does anyone have any thoughts?
Thanks,
Matt