If you don't currently have power to your USB without the GROM installed then I would be suspect that you have a wiring harness issue, or it is currently unplugged. Which GROM did you order? There a two variants for GX460. The radio unit is different for 2014+ and for the 2010-13 you need the...
Sounds like your tech is inexperienced. Every single system out there completely replaces the aux/usb port, as in the factory USB/aux ports will no longer work period. you have to supply a new USB extension from the GROM unit. I have a GROM unit as well. It's possible you got a dud. The only...
You need to go read the user manual or watch a youtube video. Your factory USB and Aux ports no longer work as you installed a unit inline to that connection making them obsolete. You need to install your USB cable to the GROM unit and change the radio function to USB so the GROM interface will...