Are you running POD Farm standalone or as a plug-in in your DAW?

Has this particular UX1 ever worked?  I'm wondering if the hardware unit is broken . . .

Since you have tried this on two different computers with the same results, I would suggest that perhaps you have a defective one.  You should take it back to where you purchased it, and exchange it for one that works.

A few more things that I thought of to try. . .

Check in License Manager to make sure that your UX-1 is authorized for POD Farm 2.51.

- if everything is OK there -

In POD Farm 2, go to File -> Preferences -> Hardware Tab and make sure that your UX-1 is selected as the device.

- if there are still problems after that -

You also might want to try installing GearBox 3.72 or PODFarm 1.12 and try it with those to make sure that there isn't a software install or licensing issue.

After all of that, if you can't fix it by turning up the output volume knob or it doesn't work with headphones, then I suggest that your hardware is defective (it HAS been known to happen, although infrequently), and you should return it to the dealer you purchased it from for an exchange.