No power to input 1

Hi,

Input 1 on my Zoom H6 will not record dynamic or condenser mics. There is no audio registering on the meter for that input at all, while the other three inputs work just fine. I’ve tried increasing the gain, I’ve tried a condenser with phantom power on, and a dynamic mic with the phantom power off but to no avail. I’d like to purchase a repair kit, but I’m not even sure what is wrong with it. How can I determine what the issue is? Thanks for your help.