SSID not seen by PC's
I am working with one of my clients that purchased an Xi-1 WAP about 6 months ago. The unit has worked fine since installation. Recently the device can only be seen by Apple devices and not by Windows. All the PC's in the office cannot see the SSID to connect to it, but all the Apple laptops and mobile devices have no issues seeing and connecting to the WAP. I have updated the device firmware to 184.108.40.206.370 and still the issue remains. Your help in this matter would be greatly appreciated.