Same thing happened to me recently. A favored breakfast place that had always posted like a well oiled machine, just stopped mid-October.

I went back 4-5 times, as AA Dining claimed it was glitch on the Merchant's side with Mastercard, that would be resolved.

Although I eventually got my points for all the visits, the process and cycling with AA Dining, got annoying and old very fast.

(Wait 10 days, submit form, don't hear from AA except the automated message, call AA in frustration 3-5 days - after all, you submit a receipt - how hard can it be -, a 5 minute call with a polite agent who promised the points would be credited, 2-3 days later points would post. Rinse and repeat.)

A few weeks ago, I received an email from AA Dining that the Merchant had left the program.

Coincidence? Who knows. I've been out of town since December but will probably talk to the Merchant when I get back & ask what happened from their perspective.