I cant save page I just created. I press "Im not a robot" checkbox and successfully pass the verification, but green tick resets to empty checkbox again and it is impossible to save changes.
I imagine that the AdBlock plugin breaks the CAPTCHA, especially if the AdBlock plugin also has a tracking protection. The current CAPTCHA tries to track you to judge if you are a legitimate user. There are multiple tickets regarding the use of CAPTCHA in the wiki: https://github.com/openstreetmap/operations/issues?q=is%3Aissue+captcha+. Your case sounds similar to #449.