Can’t change my network name

I have a Nighthawk C6220. Recently had to reset my unit. I want to change my network name from Netgear 88 to a different name but it will not allow says it cannot connect to the router yet I have perfect connections and am able to use app fine. (I have previously been able to change my network name) I am unable to do it on the Internet as it says I need to use the app so the IP address in the URL does not work. It has a USB storage port, but says it’s only for connecting a storage device not connecting to a laptop. I have reset my modem a couple times now and I still get the same message. It says “configuration error. The router could not apply your new settings.” Then it says to check for my connections and they are fine. What is the problem? Unit 3 yrs old. I reset it troubleshooting a different issue.