5ghz not working C6300v2 model.

I purchased this routers about 3 months ago. Recently I started having issues with the 5ghz WiFi not working. I cannot get a steady connection. I get an erratic, and jumpy speed on it. I have internet because I can connect to the router with a cable, and the 2.4ghz works fine. I’ve already rebooted the device 3-4 times. I have also done a factory reset on the device. I’m stuck, some help will be greatly appreciated.