Update on my solution from Get Away Today
*Note they report the deadline for re-issuing tickets is April 29th (that's Disney's deadline, not theirs)
I traded in my old 4-day Parkhoppers with Maxpass purchased Feb 2020. They issued me new stock, 5-day Parkhoppers. Because of the amount I paid for Maxpass, the new tickets were slightly less which they are crediting.
I was worried about the risk of having old/cancelled tickets with Park Passes linked to my account and a lengthy Disney call/chat to fix this. But I really wanted to avoid a trip to the ticket booths (for possible MP refund) which I am picturing being a real mess; especially if they have launched a new membership program before our trip. I also wanted to add a day, and obviously worried about not having Park Pass availability to add a day during our trip.
I'm happy to report success on all. It went like this:
1) GAT cancelled/reissued tickets in just seconds. Clearly it was just a few clicks on their end.
2) In just the time it took to end the call, I went to the App and the old tickets disappeared (sweet, no de-link call to Disney).
3) I went to the Disneyland.com and my 4-day Park Passes were still there. I cancelled all... no errors even though the associated tickets were gone.
4) My GAT emails arrived in under 60 seconds (cancellation and new tickets/invoice)
5) I linked the new tickets and booked all Park Passes with no issues (using hotel bucket/VGC)
Happy camper here and I'm a big fan of GAT. Also, score one for Disney IT/ticket system, even though it's a little goofy seeing different things in App/website. At least the database is working. Hope the front end is synched up soon.
Now, if we have issues at the gate or trying to get ROTR Boarding Groups, I will eat my words. But really, everything looks in order. It was a pleasant surprise!