UPD2 ok, I looked for web app logs in logs - debug, but not in browser console.
identified the BP that caused the problem - Request attention icon set. switched it off and the BP containing it started working. It’s not crucial now for us, so I close the topic.
UPD1 put a write to log right after the onCreate block, doesn’t work. Seems the trigger is not working on page load.
After deploy on 13th late evening on many pages endpoints are not launched any more. On newer pages it’s ok, but in /requests/ section of our app the data is not updated anymore in web app, I see that endpoints that should be launched to update the data are not launched. They are launched via web app BP (retrieve the url param) and then they trigger the endpoint.