Hi,
The reason you are getting this error is Business central introduced a new feature email view policy which give the ability to Administrators to have more control over who gets to see which emails by setting email view policies.
So you globally search User Email policy
and add the users and the policy. Currently it must be blank which means it has considered all the users to have the policy. That is why it is giving you the error.

if you want to change the user name of the user you can update it admin center and get the update user using Update User from Microsoft 365 action in user page.

If my answer was helpful to you, please verify it so that other users know it worked. Thank you very much