I was waiting for somebody wiser than myself to reply on dongles as I have never used a Wi-Fi one. I have due to an attack from the net which disabled my inbuilt network program on my motherboard installed 2 network cards one for lan and one for wi-fi . After using the set-up disc both worked. I also have a hub 4 . It is sometimes possible that the usb connection gets corrupted or just refuses to work . I take it you have tried it in other usb sockets? If it still refuses to work then I would cut my losses and buy a pci-express card and fit it in your PC. I have two usb sockets although recognised in the programming refuse to work . As I have many others I cant be bothered to investigate bought a TP-:LINK 300Mbps wireless N pci express adapter[twin aerial] and it works just fine with the HH4-100% transmission. Ditch the dongles okay for flashdrives but a bit temperamental with other things.
Try giving the 2.4Ghz and 5Ghz frequencies a different SSid on the home hub. ie add a 5 to the end of the 5GHz SSid. You will then be able to see the 5GHz and connect to that separately from the 2.4Ghz