MC288051: Microsoft has added size restrictions to Unlimited Archiving (Aka Auto-Expanding Archiving). The change will take effect beginning November 1, 2021. Once this limit takes effect, your users will not be able to extend their online archives beyond 1.5TB.
You should check the size of archives in your organization if you are concerned that they might be close to the limit.
To check Archive mailbox size, you can use the Get-MailboxStatistics cmdlet or the below script: