I have a DXP-Plus with two cabinets. In the second cabinet I have a CO card, analog station board and a T1 card. The T1 card recently stoppped working and has only 3 red lights. The circuit from the service provider seems to be working ok the CSU/DSU lights are all green and it does detect when I unplug from the T1 card. I have changed the T1 board and the new board is having the exact same response. The CO line card and station card located in the same shelf are working fine. Could this be a CSU or services board problem. I'm not sure where to go from here. Nothing has changed in the programming, the T1 board just stopped working.

I'll bet it is the CSU; they fail quite often. Remove it and connect the card directly to the circuit.