MacBook Air doesn't connect to known WiFi network automatically I have two WiFi networks: one at home and one in my office. Both are basically quite similar – same connection provider, same connection speed, same modem, same router – the only difference is that at home we use an AirPort Extreme station to broadcast the WiFi signal. 

My MacBook Air (1.85 GHz Intel Core 2 Duo, OS X 10.7.5) does automatically recognize and log in to the AirPort Extreme powered home hotspot – but it won't auto-login to the office hotspot even though it does remember the network and lists it in the Network Preference.

Is there a way to 'teach' my MacBook Air to auto-login to 'whatever' WiFi network I want? Or does that only work with Airport Extreme powered hotspots? Or does it have anything to do with the Airport Extreme anyways? Thank you for any suggestions / pointers…!
You can rule out your laptop for being the problem by resetting wifi configurations. Do Step 1, it's relatively safe.

http://osxdaily.com/2014/10/25/fix-wi-fi-problems-os-x-yosemite/