MacBook Air has stopped accessing internet wirelessly via ATT Pace Wi-Fi Modem 5268AC

MacBook Air (13 inch, mid 2012, 1.8Ghz Inte3l Core i5 Processor) will not access internet wirelessly via AT&T Pace Wi-Fi Modem 5268AC located in home office. When take to another location such as at Starbucks, it connects wirelessly with ease. Took the MacBook Air to the Apple Store Genius bar today and it connected to the internet via the in store Wi-Fi perfectly. Thorough testing was performed and no issues were found. Came back home and found the computer won't connect to internet. Also have iMac at home in the same room as the MacBook Air and it easily connects wirelessly through the same AT&T Pace 5628AC Wi-Fi modem. Do not know what is wrong or how to fix it so that an internet connection can be established for the MacBook Air. Thoughts? Steps to take?