Another thing to try would be to uninstall the Modulay then reinstall it.
Chasing browser issues on the other hand, I would try a different browser to see if that got me anywhere too. Since this relies on web browsers and those are always getting updates or having issues where one works and another one doesn’t, it could be easily that instead of the MOD Duo.
I’ve done OS jumps without issue in the past and for all practical purposes, it should be quite alright to do that. If you have an older version of the OS you could try reverting then have the Duo update again to the current version.
Those are a few things I would try to see if I could get it working.