Thanks for the responses. I have tried logging out and back in and in incognito on my computer but those didn't work.
Their reservations are showing up, just the online checkin portion is missing. They are arriving a few days after us and they have a split stay, but I wouldn't think that would be the issue. Their reservation was made in my MIL's name, I have no control over their reservation in my own
MDE account.
I did, however, book one of their stays using my past guest offer code so maybe that's the issue??