AC1200 - I JUST MOVED IT AND NOW CAN'T RECONNECT. ;-(

THANK YOU for your very informative reply, and i'm sorry mine OP was so lamely vague. Here's some more info:

First, i have the AC1200 Wifi Range Extender model EX6150v2...but the "associated products spot above wouldn't allow me to enter that. It only showed the EX6120. (SN #4LV91954A4A26)

I bought it four months ago, did a "quick install" - and now i'm not even sure how i accomplished that - i THINK through the NightHawk app - and my wifi service SEEMED to be better for a time. Though lately it's been back to terrible again, so i thought i would reset the whole thing. I unplugged it and moved it back to my office (near my Arris D13D modem/router). Started through the instructions: plug it in to an outlet near the router, wait for the green light...and then i didn't know my passwords for the network, the router, etc....and that's kinda where everything went bonkers. I tried resetting the router, and just then could never get anything to connect. I googled a bit, found out that my customer service with NetGear ceased a month ago (i had realized there was a 3-month limit), found the support community and here i am.  😉 

Again, thank you for your reply. 

I will go through all the reset steps you suggested and see if this gives me a light at the end of the tunnel.