Can't recover my wiefiext.net password because error says clue answers wrong

Installed a new modem at which time range extender no longer functioned.  it is connected by ethernet cable.  Followed Netgear instructions, but couldn't sign on to mywifiext.net. Don't remember password and when tried to recover my answers to security question were rejected.

Need to recover passwork or set new passwork. Need alternative to security questions.