GPT 4 permanent error - it opens a white popup and doesn't work

I am a Plus user for many months, for the last 2 days in any browser I see first “This is a free research preview”… with few steps, just next and next…
And later when I ask any prompt - I see a white popup window, with X above, but it’s not possible to close… Nothing helps.

Meantime GPT 3 works fine… Does anyone could advice?