Able to show paid apps with Market Unlocker, but unable to purchase? The root cause is Market client on phone does not sync up billing data to backend server properly.
To resolve this, we need additional steps to force market sync up. Here the steps:
1. Switch phone to flight mode
2. Enable Market Unlocker and Auto Unlock option (make sure the app is installed in internal storage instead of sdcard)
3. Got to system Setting => Applications => Manage applications => All => Market
4. Reboote phone
…make sure wifi/3G is turned on…
4.1 (Inserted on Feb 22nd 2013). Configure and enable proxy after market unlocker has been enabled automatically. Recently google play was updated which detect user ip address as well as carrier. It’s similar to Amazon appstore. Please enable proxy.
5. Wait google gmail sync up completed. You can check gtalk status as well.
6. Open Android Market. and it should be able to purchase now.
It might take a few hours to take effect on some phones depending on the installed android system. So you might put it there and see if it works tommorrow.
Still failing? You may try revert Google Play/Android Market to older version (say 2.x), and do the above steps. It will must work. And you can buy apps what you want.
After able to puchase (failed again? impossible), upgrade to the latest version of Google Play Store if you like the new markets.