Issue joining Wi_Fi, Motorola SURFboard extreme sbg6580?

Hello! So, here's my issue. My family has recently bought a new Motoroal SURFboard extreme sbg6580, it's working great through ethernet, but nobody can connect to it with wifi? It's not connectable through cell phones, laptops, etc. unless in ethernet. It's says "Invalid Password" or "connection TImed Out" But I have changed the password and double checked multiple times, it works fine when logging into the thing where you change the password and sutch. Please help! :c