I’m also having this issue with the Google Drive extension with multiple emails.
The error from Google is:
“This app tried to access sensitive info in your Google Account. To keep your account safe, Google blocked this access.”
I’m having the same issue with the Gmail API and found this thread:
https://ww.wp.xz.cn/support/topic/php8-0-ajax-error/
In my case, the function base64_decode() was disabled on the server for security reasons. Enabling it fixed it. I don’t believe I received a cURL error though.
Is this plugin still maintained?