Marriott Rewards (including Ritz-Carlton) - Marriott summer promo

I made a reservation for the South Beach Marriott. Of course after making the reservation, the summer promo code came out which gives you a $50 daily credit. Does anyone know if they would add that promo code to my reservation. We are new to Marriott rewards. The promo code is SUM. Thanks

Can't you just make a new Res with the promo code and then cancel the old one?

Can't you just make a new Res with the promo code and then cancel the old one?

I suspect the res is nonrefundable.

Even if the rate is non-refundable, you can still go in and modify the reservation and get lower rates or promo bennies like this one. The only time you can't do this is if the rate rules for the rate you booked says no changes allowed.

I have changed ADP non-refundable rates before and the a credit for the difference up on my folio.

That's good. Here in the UK the same rate code provides "Great summer rates" get 20% off restaurant spend, excludes room service,bar or mini bar. Fairly useless really. If that is the best offer Marriott can come up with after a spring of 15% of Stay for breakfast and other uninspiring "offers" then it is a pretty poor show for Plats

I'm trying to book for this weekend and get:
The special rate you selected is not available for the dates you requested:td: