| | 10-21-2011, 10:32 AM #1
I can't 100% certify this trick works or what is actually causing it to work for me but I was able to update from 7390 to 7392 to 7403 to 7720 using this trick. I did notice that I did not have to use these steps to update from 7403 to 7720. That update notification came directly after 7403.
1. Make a backup of your device using the Windows Phone Connector. (Or not. Depends if you mind downloading all your apps again or not.)
2. Reset your phone to factory default.
3. Set your phone up with a Windows Live account.
4. Make sure your carrier's APN settings are correct. (Found under "Cellular" in "Settings")
5. Let the device bring down all your info (Xbox Live account, Email, Contacts, etc.)
6. Connect your phone to the Windows Phone Connector and perform a sync.
7. Select "Device Options" and select "Check For Update". (No need to shut off the network connection. It should notify you that you have an update available.)
Some of these steps may be unnecessary but these are the exact steps that worked for me. Good luck.