What do you mean by "apps site"? Do you mean the Google Play Store or something else?
If it's the Play Store my best guess is to check that your Google account is set up correctly on the device. I think it also requires background data to be enabled in the system settings.
Otherwise, please post again with more information. You'll need to register (which is free) to reply to this thread, otherwise just post another question with as much information as you can.