cannot connect laptop to my netgearunite 770s hotspot device

not the aircard but the at&t unite 770s hotspot device , i'm 64 and don't really know that much about techy stuff but last month on Ebay i purchased the 

Netgear Unite 770S 4G LTE Mobile Wifi Hotspot - Black (GSM Unlocked) L/N

and through Ebay also purchased an at&t perpaid sim card to use in the unit  . I inserted the sim card correctly , turned the unit on , went to computer to select unit wifi address and entered the password , it did its thing but did not connect me to the internet . I tried to connect through the unite manager when it directed me there on its own but still could not connect and now that doesn't even pop up anymore , even entering the url address given att.com/unite ... tried googling and even asking for help with the Ebay att seller to no avail ...  I was also told to go intonthe unit settings and reconfigure the apn , only when i go into the hotspot unit in settings there is no such option . Please help