If you have access to the Metabase database, you will find the email settings in the “setting” table and the users are in “core_user”. You can make sure that the outgoing email is set and also try changing the user settings.
For example, start a new Metabase and copy the core_user row that you can access with there into the database you can’t get into.
Please make copies before trying the above. I have not tried it. I am just throwing ideas around in case that helps.
Let us know how it goes.