GroupMe login problems

Guys, I'm not sure if I can address GroupMe problems in this forum, sorry.
Having run Groupme as an app on my win 11, 25H2 desktop for years, my PC surprised when, about 3 weeks ago, it refused to open the app. Login failed. I contacted their chat bot several times but did not get any response that would solve the problem. I contacted the GroupMe tech support several times via email but nobody ever responded. I uninstalled and reinstalled the app, no dice. The new install, when opened, shows the login screen, asking for phone or email and pw without even giving me a chance to set anything up. I found out that MS has problems with GroupMe login but, after 3 weeks, one would think they would have found a solution. Has anyone any idea what could be done to get this app to log me in?

i found this which may explain things and help with log in

best of luck Steve ..

Thanks for that link. However, I have done all those things several times over but nothing worked.
The most galling is that their support has not responded in weeks. not very nice support.

Just wanted to add something:
When I start the reinstalled Groupme version it opens immediately to the login screen, already populated with the earlier phone/email and PW.
Apparently, uninstalling the app does not get rid of certain files.
How can I find remnants and traces of the earlier install and delete them manually?
I need to get this thing going. It's a group I have started several years ago and it's really laughable that I can't get access but everybody else in the group.
Way to go, MS!
Btw, the last part of my previous post: "not very nice support" was expressed a bit more drastic, but it seems that some kind of censor has altered it. So much for free speech!