Help - Ensoniq SQ-R sustain problems

[StuartAberdein]

I have an Ensoniq SQ-R (rackmount version of the SQ-1). I haven't used it for a while and the sustain now doesn't work. I have tried the MIDI keyboard (Ensoniq SQ-80) and sustain pedal with a Roland Soundcanvas and the sustain works fine. However on the SQ-R the sustain pedal (plugged into the SQ-80) has no effect.

The SQ-R is obviously not seeing the MIDI sustain message coming from keyboard. It must be a setting but I have hunted through the manual and can't figure out what to do.

Can anybody help?

Thanks,

Stuart