Q: why my apple id can't download purchased apps

Hi linhsubeo,

Thanks for the question. I understand you are having issues downloading an application from the App Store. To troubleshoot these issue, let’s follow the steps for iTunes Store connectivity:

First, try signing out of your account in Settings > iTunes & App Store. Once signed out, go ahead and restart your device. Once your device has restarted, sign back in to the iTunes Store and try to download the update.

iOS: Changing the signed-in iTunes Store Apple ID account

http://support.apple.com/kb/HT1311

If the above did not resolve your issue, refer to the following:

Can't connect to the iTunes Store

http://support.apple.com/kb/TS1368

Thanks,

Matt M.