Unable to convert regular mailbox to shared mailbox.

[PK Player]

Hello.

I have a user account I set up some time ago in Microsoft 365. We use a hybrid setup where I add and configure a new user's domain account on a Domain Controller in our office and it is synchronised with Microsoft 365. I then assign a Microsoft 365 Standard license to their account via the MS 365 Admin Center and they are ready to go.

I wish to convert the user's mailbox to a shared mailbox but the option to do so is not present.

When I open the admin console and select the user from the Active Users list, then select the Mail link there is no option to convert to shared mailbox.

If I choose the main option to open the Exchange admin center (simply listed as 'Exchange'), the admin center screen is briefly displayed, then my own account is shown. I am unable to view another user's exchange account properties.

If I choose the option to edit the user's Exchange properties from the list of users on the Active User's  Mail screen I get a message stating I don't have permission to do so and that I should sign out (which I have not done yet).

My account is both domain admin and MS 365 admin. Note that my MS 365 admin login uses Email address removed.

Can anyone help me resolve this issue, please? I was able to do this about a year ago but do not understand why the option is no longer present. I have looked at other user accounts and see the same - no option to convert to a shared mailbox.

Thank you.

[#2]

The system removed an obfuscated address. I was just confirming I am using an onmicrosoft.com email address to login to the MS 365 Admin Center.

[#3]

Not sure about the M365 Admin center, but the EAC will allow you to convert a mailbox to shared, regardless of whether it's synced or not. If you are having trouble with the EAC, try switching to the "classic" one, or do it directly via PowerShell.

[#4 · Accepted solution]

Thank you for replying.
Accessing the classic EAC 'normally' resulted in the behaviour I described above using both the new and the old Exchange Admin Center. What I had to do was enter the address for the classic EAC (https://outlook.office365.com/ecp) into a private browsing tab, then log in. I was able to see the recipients etc. after doing this.