Email notification stop working

Hi.
I am new to Appsheet. Yesterday i started to design my Email workflow with PDF attachment.
As Google doc has some problems with the design i need to test and sent the workflow a few times.
But now the workflow has stop sending. Can someone help and guide me how do i troubleshoot this problem or is there a block from Gmail as its the same email has been sending every 5 min?
I have check my spam folder but its still not there. I guess the workflow has stop working. I did not change any setting as its been working when i test it. I only change my Google doc design. I even tried to sent the workflow without the PDF attachment but still it does not work.

Someone pls help. Thnx