I have an iMac 27 inch 2014 model and when I try to connect to my BTHub 4 and it doesn't connect! I use the correct password and when I try to connect it says 'Can't Connect' error thing. But when my Apple Macbook Air connects it has no trouble. I am on Yosemite on my iMac, though I have bootcamped it and on the windows side the mac connects to the router but on the apple side it doesn't! So when I am on my mac side I have to use an Airport Extreme to be the router and ethernet that to the router! PLEASE HELPP!!!!
Try turning Smart Setup off.
Also try separating the SSIDs.
Devices where there are known to be problems include:
If you haven't already, you could try to create a new location: System Preferences>Network>WiFi - choose Location>Edit Locations. Click the '+' sign to create a new location and give it a name. Select it and select 'Done'. Give wifi a few moments to establish a connection (sometimes you may need to turn wifi off and then on again to force the connection. Hopefully the new location will show as green. Test to see if it works. If it doesn't you can return to the Automatic option that existed before these trouble-shooting steps.
You can also hold the Alt (Option) key whilst selecting the wifi icon (if it's displayed in the menu bar) and choose Wireless Diagnostics there.