Well it sounds like some digging's required which would suggest to me that there's a problem with the D-side cabling somewhere between your house and the exchange/cabinet.
An inability to sync would make perfect sense if this part of the circuit has been completely severed.
I can't allude to what the specific problem is without escalating through Wholesale which our Faults guys are much better positioned to do. Regardless, I don't think it would help speed up resolution. Sounds like there's a few people affected by the problem.