The "This trigger has been disabled for an unknown reason" error message typically appears when Google has automatically disabled a trigger due to a policy violation, such as exceeding the maximum execution time or sending too many emails. However, in some cases, triggers may be disabled for unknown reasons, and this could be a bug.
Here are some tips that you can try to resolve this issue:
Double-check your code for any errors or issues that might cause the trigger to fail. Ensure that all the required permissions are granted, and there are no syntax errors in the script.
Try creating a new trigger with the same code and see if the new trigger gets disabled. If it does, it might be an issue with your code or an issue with Google. If it doesn't, then there might be a bug with the original trigger.
Check your G Suite account for any issues that might be causing the trigger to fail. For instance, check to see if your account has been flagged for suspicious activity.
If none of the above solutions work, contact Google Support for assistance. They may be able to help you identify and resolve the issue.
I hope these tips help you resolve the issue with your trigger.
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Nerio Enrique Villalobos Morillo
Buenos Aires, Argentina