Informer(terminal) modem problem

I have an Informer terminal (emulates vt100) that seems to be working o.k. except that when I dial out It rings once, twice, rarely three times and then reports no dial tone. The phone chord is fine. I thought that perhaps it wasn't making a connection with the socket so I did some wiggling around with it but to no avail. The manual that came with it is actually wrong about the machine in terms of how to enter setup for the modem, and I have no idea what the modem speed is so that is a problem as well. I assumed first 300 bps and it initialized but still the problem with the loss of dial tone. It also initialized at 1200 but the same problem. This is from 1983 so I figured it was probably 1200, maybe 2400, but I don't know. I tried it on tone AND pulse, but nothing either way. The modem is not removable as its basically the bulk of the electronics. It does offer a serial port which I will try but don't have an external modem on hand. Any idea why the loss of a dial tone? TIA colan