cgoro

The issue was resolved

The secret value has not expired.
I have cleared the settings URL of any parameters but the Fatal Error is still recurring when I attempt authorization.
The second error about the invalid grant is no more.

The error displayed on the plugin page:
invalid_grant AADSTS54005: OAuth2 Authorization code was already redeemed, please retry with a new valid code or use an existing refresh token. Trace ID: 1bbf59c6-5e03-4829-8575-5fb577997700 Correlation ID: a8f59c80-054d-4bc9-ac40-9bb5e670cbf7 Timestamp: 2022-01-19 13:38:10Z

Thanks @edwardcross the plugin is working after reauthenticatication

Thanks.
So far the experience with your plugin is awesome

Sorry. Intended it for gravity forms

I deactivated and deleted the plugin and reinstalled it after a day and it’s working okay and sending all emails.

I had checked the Keep Oauth Credentials box during the initial installation which I believe stored the credentials for that installation which my new installation credentials appear not to be able to replace to allow the plugin to communicate with Ofice 365

The below information appears on the configuration page of the mail integration plugin:

Deactivation Options
You can choose to keep your OAuth credentials within the WordPress database after plugin deactivation below, in case you are only temporarily deactivating this plugin. The default is for your credentials to be deleted.

Could anyone know what is the name of the table in the WordPress database that stores the OAuth credentials for the mail integration plugin?

Yes, I want to reconnect the site to Office 365. Since March this year, I have been using the mail integration plugin for sending emails from the site till yesterday when it stopped which prompted me to reauthenticate the plugin to try to sort the issue. The fatal error popped up during the reauthentication

Thanks