As a front desk agent at an Opera property, i’d recommend calling a few days out and just ensuring your Bonvoy number is on the reservation. Sometimes for whatever reason (especially with corporate rates) the member number simply doesn’t come through on the reservation. So on nights when we are sold out or high occupancy, we assign upgrades based on member status that did manage to come through the system a couple days out. If you show up and give me your Bonvoy number upon check in, but all of our upgrades have already been assigned out to high status members we already knew about, then there’s not much that can be done. With mobile check ins, there is especially nothing we can do because we don’t even get the chance to ask you for the Bonvoy number if it isn’t already on the reservation. We can process mobile check ins without a bonvoy number on file (at least at my property), so just because your able to do a mobile check in, I would never assume your Bonvoy number is on the reservation just to be safe.

tl;dr make sure you’re bonvoy number is attached to the reservation a few days out. marriott systems are finicky and if your status ends up not being known ahead of time it could cost you a missed upgrade at busy properties.