Have you tried using a private/incognito window for Choice or deleting all Choice website cookies from your browser?

I have seen weird problems on the Choice site of various kinds that were resolved by deleting cookies and then logging in again or by using a private/incognito window (which ignores all your cookies).

But, yes, it could also be that they have some limit on how many reservations they can display. Most people don't make oodles of reservations all at once.