We've got a web form that has, for years, worked just fine. An applicant fills out the form and upon hitting Submit, it gets sent to a GMail address and to a spreadsheet on the GMail address's Google Drive.
This week, it stopped sending to the GMail address, but the spreadsheet was getting updated.
The GMail address is able to receive email (sent from my non-GMail email address), so there's nothing wrong with the address. and there's nothing in the SPAM folder.
When I changed the destination GMail address on the form to MY personal GMail address, I received the form AND the spreadsheet on the original GMail address's Google Drive was updated.
I changed the destination email address back to the original GMail address, resubmitted the form, and did not receive it, but the spreadsheet DID update.
We have another form on the site that also gets sent to the original GMail address, and that one also does not submit the completed form to the GMail address (and oddly has never created or updated a spreadsheet on Google drive). I think if the first problem gets solved, the second form will solve itself.