Office 365 (Outlook on the web) - Account Access Error
When you attempt to open another mailbox (user or service account), you may receive either of the following errors: receive a '404' error:
The reason you are receiving this error is because you do not have the proper permissions to the account you are attempting to access.
You will need to contact the owner of the account and ask them to grant you full-mailbox permissions.
For user accounts, have them follow these steps: Office 365 - Manage Full Mailbox, Send As, and Send on Behalf of Permissions
'something went wrong' error
The reason you are receiving this error is because the service account may have been just created/updated.
Please wait about 60 minutes and try accessing the account again. If you continue to have issues accessing the account, contact your domain administrator or the DoIT Help Desk.