Sometimes it takes a while. I'd give it a few more days. I think a lot of the hotels run their batch processes on Sat/Sun, so hold out until then.

Then you can email MGM member services with your info -- at which point they still won't do anything for you, but will at least confirm whether or not your Hyatt number was properly tied to your reservation. Then at day 30 post checkout -- if it still hasn't posted, you can email MGM again and they will submit a retroactive credit request for you. The credit will hit a few days after that -- MGM is diligent about following up on that.

Historically, I've found that I usually get my stays in 5-7 days if things are working properly. If not, then settle in for a long waiting game. It's quite the PITA. You'll eventually get your credit, but they won't do anything for you until the 30 days is up.