My ac1200 6120 won’t even even connect to my wifi router anymore

R6120? EX6120

Firmware on it? 

Modem/gateway its connecting to? 

The R6120 doesn't connect to your wifi. It broadcasts the wifi and devices connect to it. 

but if its a the EX6120 its an extender and does connect to wifi and rebroadcast it. 

See how details are key to helping? 

So go over what you have in detail, what its connecting to, whats actually happening, even the led's on it can help. 

the more you tell us, the better we can help.