Unable to Enable Archive mailboxes from the Security & Compliance Center Admin Site or ExchangeOnlin

I was able to access https://protection.office.com/ site so as to enable online archive mailboxes for a few users whose mailbox size was growing big at a rapid rate. I used the steps in this link; https://docs.microsoft.com/en-us/office365/securitycompliance/enable-archive-mailboxes

However, currently no Global admin account is able to open that Security & Compliance site; we just get a blank white screen despite having full/direct internet access.

Also, when we try to enable the archive mailbox for a user via EMS, we get the error below.

I have tried to research the error, and some websites say I should enable archiving of a user from on-prem exchange ECP. However if I do that, it enables the archive for the user’s remote mailbox but still fails on the exchange online archive, and also changes the email address...