Powermax PMTS-50 Transfer Switch not engaging

when power is available on the "generator" side of the switch, the green LED lights and the thing buzzes really loudly (didn't do that before), but contactor never engages to connect to the load side. I've tried setting the jumper to bypass the delay but it does nothing.

Before i call Powermax (i think i'm a couple of months out of warranty) - is this common for these to fail? I have general/definite purpose / HVAC contactors in use for home automation purposes that have been in service for years without failure.

thx in advance