Their database does go down sometimes (so denies your number even belongs to them!), and sometimes forgets about the fibre stuff. If the data comes back later today or tomorrow, it will have been something like that.
Sometimes the predictor changes, and your predicted rates become too low - and the checker stops reporting them at all. This one will be harder to overcome.
What speed was it predicting for you before it went AWOL?
Which checker did you use? Do these two give the same story:
I've been through very similar pain - where my cabinet was there in October, exchange was reported as live by BT in November, and the surrounding cabinets went live in December. But our cabinet took an extra 2 sets of roadworks, and 3 months, to get the power sorted out. The dates did the same as yours, but then suddenly swapped to being live 5 days ago.