I have a Lumia 521 to be used as a wifi only device. I can get on wifi and browse or do other things but when I go the Windows app store and try to sign in to download an app it won't let me sign in to my account saying it doesn't have sufficient reception. It does this with an unactivated sim card installed or no sim installed. This tells me the store is trying to use cell service to sign in. Others have said they using this phone on wifi only and have no problems. What am I doing wrong . . . any ideas?