Marriott Rewards customer service is the right place to start. In my experience (situations like yours), they will call the hotel to have them add the points. If they need to, the hotel will call you directly. Sometimes it works great and the points post in 24 hours or less.

Other times, you end up making multiple phone calls, and it is extremely aggravating, and the points (usually) post a week later.

This is my biggest complaint about the MR program.

Good luck and try to be patient.