Non Microsoft registered email account, working since Wunderlist, stopped to work. Any inside?

I had worked with ToDo, since Wunderlist, back at least to 2016.

I registered my profile to Wunderlist using my email from @netzero.net domain, and it worked perfectly, even after Microsoft absorbed Wunderlist with the ToDo name.

Two or three days ago the sing in stopped to work and I'm getting the below message:

Any ideas will be appreciated.