Είχα και εγώ το πρόβλημα και ακολούθησα τις παρακάτω οδηγίες:
From the Start screen on your Windows Phone, flick left to the App List. Scroll to the Games Hub and note whether the Games Hub icon says Xbox LIVE or not. If yes, continue with Step 2. If not, skip to Step 5.
Tap the Xbox LIVE Games icon to open the Games Hub.
Tap More More icon, then tap Refresh. You should see Updating... on the top-left of the screen.
Re-open the Marketplace Hub. You should no longer see the You must install the Refresh Marketplace App notice, and you should be able to see various featured apps and games. You can now continue to use Marketplace—enjoy!
If you continue to have problems, do the following:
Plug in your Windows Phone using it's wall charger, ensure your phone is connected to a cellular data connection or Wi-Fi, and charge your phone for at least 24 hours. During this time, your phone will automatically attempt to connect to the updated online Windows Phone Marketplace infrastructure, after which you should be able to continue using Marketplace.
Δλδ, κάνουμε refresh στο XBOX-LIVE και μετά συνδέουμε το κινητό στον φορτιστή με wifi και gprs ανοιχτό. Σε εμένα, μέσα σε 1 ώρα είχε διορθωθεί το πρόβλημα