MAX - "Can't verify subscription"

@CoCo2023  The sunset date for HBO Max and AT&T was Dec. 5th. Discussions on what would happen have been going on for at least 6 months. Basically it's this:

AT&T no longer has control over HBO Max (which has now been rebranded Max) since AT&T spun it off as its own company. The "free" HBO Max accounts were supposed to be migrated over to Max but it has been one giant cluster****. Some account did, most didn't. The problem is the respective IT departments can't seem to figure out how to get AT&T login creds for the accounts that still qualify for the "free for life" Max to be recognized by Max. Apparently Max wants its own logins but the migration to create those new logins is difficult. AT&T has been able to get some accounts fixed and those that got fixed were able to get the Ad-free, two concurrent devices, full HD only level. If you still want the 4k HDR/Atmos level then you need to subscribe directly to Max and pay for it. There is no upgrade path (paying the difference) offered by Max or AT&T. 

If you haven't made ANY changes to your existing account since you first activated HBO Max, then you should still be able to get Max albeit at the new HD only tier. However, that is now up to Max and how long they will continue to honor the legacy AT&T accounts is up to them. If you read your TOS you'll see that promos etc are subject to change and this transferring from one company (AT&T) to another company (Max) certainly falls within that caveat. All you can do is keep bugging AT&T to see if they can fix it on their end so that Max recognizes you without having to create a new account which you would be charged for.

I suspect that this won't be fixed one way or another until sometime after the first of the year.