So my DH actually spoke to a female in tech support this evening. My DH is an IT Director for his job and I thought it wouldn't hurt to have his technical knowledge for the call. The technician confirmed that they are aware of the problem and that it is an ongoing project. They do not currently have a project end date. They do not have a very good idea of the number of accounts the problem is affecting, only that a certain percentage of accounts no longer show their dining reservations in the list format.
I tried to adjust an ADR and it will display under the dining reservations link for about an hour, however, it vanishes from the list as well. I do continue to receive e-mail confirmations and I checked them all last night and they are all still there, they just aren't showing.
The technician urged my DH to keep checking as they are working on it. Please keep me posted if you hear anything further or if your list becomes available.
I'm sorry you are experiencing the same difficulty, but I am relieved to know I am not the only one!