Dear Valeria Sgarlata,
Good Day and Thanks for posting in Microsoft community. Thank you for your Feedback.
Use this method if you want to view and manage the email for the shared mailbox in its own browser window. This method also lets you receive notifications of new items in the Inbox of the shared mailbox.
- Sign in to your account in Outlook on the web.
- On the Outlook on the web navigation bar, click your name. A list appears.
- Click Open another mailbox.
- Type the email address of the other mailbox that you want to open, and then click Open. Another Outlook on the web session opens in a separate window, allowing access to the other mailbox.
**Tip:**If you mistype the email address of the mailbox, the result is "No match was found". Try typing the email address again.
We would ask you to send video or screenshot about the entire process, so we can check the situation.
To protect privacy, kinldy provide screenshot/video in Private message.

Thank you so much for your precious time. Stay safe and healthy.
Microsoft Community