Here, check the recent logs which may show possible errors related to the shared mailbox.
The standard accounts like and are some typical example of the shared mailbox where the user can send or receive messages without needing a second pair of username or password. A shared mailbox is an extremely useful secondary mailbox which facilitates the user to access the shared data. One issue which arises after the migration is that some users do not view the Shared mailbox in Outlook.
Sometimes it happens that the end user is not able to view the data at the local Outlook application. Generally, the transfer is quite smooth, and there are no significant hurdles which interrupt the process and stop it. In recent years, the migration from the on-premises Exchange environment to Office 365 or cloud environment has become a trend, and many organizations are migrating their data completely to the Cloud.