forgetting my wifi password

I called support we reset the gateway to factory resett cause I took my wifi pw out thot I knew it .  Well I didn't.  

Now I'm back to square 1   it's detected my network as tmobile-76bc  now its asking me for my password   I've put in the wifi password  , & the 

AdministrTor pw  it's still not working it won't accept either of them .  Says it's wrong password what does it want me to do?