Starting from Windows 8 the connection to the GPS receiver is no longer supported by COM Ports. Instead Microsoft developed what they call 'Windows Sensor and Location Platform'. This platform eases the connection to the many location techniques that are available on the device like Wi-Fi triangulation, IP address or GPS device. This is a quite new platform and a some hardware vendors support both modes.
O ArcGIS Mobile 10.2 does no yet support this functionality which will only be available on the second quarter of 2014.
For now there are two workarounds for this problem:
1. Install ArcGIS Mobile 10.1 or 10.2 with Windows 7 and connect to the devices COM Port;
2. Install ArcGIS Mobile 10.1.1 with the ‘Location API Connection Extension for AGM 10.1.1’ provided by Esri.
I have tested option 2 on two devices and it works fine. This extension does not work with ArcGIS Mobile 10.2.
This extension comes with a readme file that states 'Copy files inside ReleaseAssemblies Folder into C:\ProgramData\ESRI\ArcGIS Mobile\Extensions. ArcGIS for Windows Mobile tablet application will use Location API instead of COM port.'
If you don't have this path on your device, just create it and copy the files. Don't forget to restart ArcGIS Mobile App. Then go the GPS Settings and Status and check the Windows Location API Settings.