So being told this is a windows issue, but I'm not sure how.
I've been beating my head against my desk with this for weeks now.
any advice would be appreciated.
In dotnet applications developers can build their applications against different version of .net.
As we know, the gazzilion .NET versions is a mess. So to alleviate the mess the application have config files with redirect bindings so you can decide which version of .net the application should use - even if it was intended for another version.
Since you don't have 4.0 you can try and redirect to 4.8 instead.
However you can also install 3.5 on Windows 11 and redirect to that, which I think maybe has a higher probability of succeeding. Since 3.5 is backwards compatible with 2.x and 3.x applications and it looks like your application originally required version 2.x.
There is actually a good chance that just installing 3.5 will solve your problem, because there are automatic redirects going on as well. (But undo your changes to the config file).