From a Starwood Lurker in another thread, it’s possible that there are no available suite/premium room options available, which apparently now precludes application of SNAs. According to the Lurker, in such circumstances, the ability to select the SNA isn’t even now available. That might explain why there is no option to apply any SNA.

Knowing how many glitches remain with the Marriott IT, however, it also seems plausible that this may be an IT glitch. The only way to know for sure is to contact the Platinum desk or message the Lurkers to investigate. You’d also likely do yourself a service by identifying the specific Renaissance property so the Lurker has the chance to respond here in thread.

If the Lurker explanation is correct, that obviously means you can’t be “waitlisted” for the upgrade assuming there is a cancellation, as some have pointed out. But it also means that you may be wiser to not waste the SNA when your chances may be just as good (or bad) as the complimentary upgrade on arrival and check in.

See my post above. I drove myself crazy trying this same thing and finally turned to my Ambassador who herself had to turn to a colleague who knew how to successfully apply. She reported that this is a known issue Marriott is working to resolve.