"they've identified there are no signals being sent on the line"
Wha' ?
I love some comments from ISP's....
No signal ? either it's a faulty card or port at the exchange which is normaly determined by clipping on at the exchange. With LLU equipment then I suppose if there is a card with nothing but faulty ports then the ISP coild deduce a faulty card. In which case a transmission engineer at the exchange.
How many times do i get a fault where the problem is the end users equipment or internal wiring yet the ISP has catagoricaly said the the end user there IS a fault on the line..... but no there isn't
With an LLU I would check sync at the mdf in the exchange, then stick a 60db load on and retest to make sure this is ok. If there's no sync on the mdf then it's a case of clipping on the llu output to make sure it's not the wiring between there and the mdf. beyond that It's up to the llu as to what to do next. with BTw equipment then it's straight to a lift ? shift.
If all is ok at the exchange then it's the NTE test socket and work outwards from there depending on what is found: either have I got sync and then the line stats