I am being asked repeatedly for an administrator name and password each time i am removing a wireless network name one right after

I am trying to delete all the old network names that have been used and show up in the advanced settings area of my wifi settings. Maybe its not necessary to remove them but our AT&T fiber gateway keeps dumping off of the internet. As soon as I log back in again to access wifi it will connect and tell me the signal is strong. I have reset and also unplugged the darn gateway and it keeps doing it. When i use the AT&T Smart Home app is doesn't tell me what is wrong. I am about to pull my hair out!