I had the same problems after update to fix the seatable connection (watch the new rows) to email client due to this error:
“This endpoint is deprecated. Please migrate to the API Gateway: Important Changes to the SeaTable Cloud API in Version 5.3”.
I tried to fix it in the current scenario but it did not work so I deleted it today and created a new scenario with a new API key in seatablea and finally it is done !!!
Do it like thousands of other people who have used SeaTable to develop powerful processes and get their ideas and tasks done more efficiently.