x14 R1, WiFi not working on 5GHz connection

So I have been using this x14 R1 for some months now and I have been having issues  using WiFi. I have an Apple Airport Extreme router and it sends 2.4GHz and 5GHz on demand to any device connected. But somehow on this laptop it just did not work at all. I got another router which sends these frequencies separately and 5GHz connection just connects and says there is no internet. I use the 5GHz connection on my phone, iPad and my girlfriends phones are connected to it. I don't understand what is the problem? Is WiFi card faulty? I updated the drivers, ran hardware and software scans for any errors/issues. I even tried deleting drivers and reinstalling them, did not work. Is there anyone who can even direct me what to do? I don't want to return this laptop as it is my only computer at the moment and I use it daily. I am even willing to change the WiFi card myself if it comes to it. 2.4GHz seems to work fine even though speeds are over 50% slower.