Wireless lost ability to use 5GHz (PCE-AC68)

Solution 1:

I had the same problem as you, and I just found the problem. The 5Ghz network was setted to choose automatically the channel, one day it changed to a channel with an high number and my card wasn't able to find the network anymore.

So just check in your router if the network has an high number channel and change it back to a lower one (now I'm with channel 40 and it's working fine) and check if you can now find again the network.

I've also open a bug report in the bcmwl package page, if this is the problem click on the "This bug affect you" button in this page

I hope I have helped you.