I had this problem with one user, but I was able to resolve it by refreshing the browser cache (control + F5). This issue occured using Edge. No such issue with Chrome.
We are having the issue across all browsers unfortunately. Microsoft Product Team are currently applying a fix and I'm waiting on an update and resolution for testing with our customers.
I'm also having problems signing into the app still.
When try to sign in with my email, it says to sign in with your work or school email address. It is definitely the correct email for my account and I had no problems last week.
I can eventually sign in after uninstalling the app (android) and re-installing, but I think this is more due to a wait time after saving and publishing the app as I was able to sign in ok after waiting a while also.
I'm also problems connecting to my SharePoint lists when I eventually am able to sign in.
I've got the same issue. I posted something about it yesterday - but presumably didn't communicate it correctly given the lack of responses. Is this happening to everyone?