When you want to enable the archive mailbox for all or multiple users in your organization you can better use PowerShell.
Note:Make sure that you have installed the Exchange Online Module before you continue. Connect to Exchange Online PowerShell – BEMO Docs (bemopro.com)
The online archive mailbox needs to be enabled per mailbox. The advantage of PowerShell is that we can easily select all users or a group of users. First, open PowerShell and connect to Exchange Online:
# Connect to Exchange Online
Connect-ExchangeOnline -UserPrincipalName email@example.com
To enable the archive mailbox for a single user we can use the following PowerShell command:
Enable-Mailbox -Identity firstname.lastname@example.org -Archive