Hi this is a long shot … the microsynth i have has 2 trim pots one is for gain.
if the gain is too low and the signal is weak you will get no sound (my fender is week but my humbuckers in epiphone is strong)
there should be a hole in the bottom of the unit… get a phillips head swrew driver and turn the trim pot.
That worked for me when i got it.
the other trim pot you have to open the unit and i have no idea what that does.

the other idea is the bypass footswitch is stuffed… if so thats really cheap.
hope this helps .. let me know how you go

-Ryan