If you receive an "incorrect credentials error" even after entering the right credentials when connecting your Amex account, try these steps:
Go to the American Express website on a web browser like Chrome or Safari (outside the Gather app, ideally on a computer).
Log in.
Navigate to Account Management > Security & Privacy.
Reset your Amex password by clicking Change Password. Follow the steps to the end.
Come back to Gather. Then re-connect using your new Amex credentials.
We have seen this work consistently for a number of customers.
If you have continue facing issues even after trying these steps, please reach out via live chat so we can help troubleshoot further.