I did not set cron to use PHP8, but PHP 8 is the only PHP version installed? Is there something that needs to be changed?
I cleared all the settings, deleted the app registration, uninstalled the plugin, reinstalled the plugin that comes with the 1.17 download (has an earlier mod date). I reset everything back up making sure not to specify "INBOX" as it is default. The setup and authorization went smoothly...it is still down though. I am searching through all the system logs now and looking in our tenant for any errors.