I have an ATA connected to an HP M3035 MFP that we recently migrated from a Nortel Meridian PBX. When we dial the extension (either internally or externally) we get differ behaviour. Sometimes, it will answer quickly (very rarely though), other times it will answer after 7-10 rings, and then most of the time, it will not answer at all. I have replaced the ATA, the network cable, and the telephone cable, but nothing seems to help. I have also verified that I am receiving ringdown at the ATA port.
Any suggestions on troubleshooting this?