Try going into Settings > iTunes & App Store and turn on “Apps” under Automatic Downloads, then check if your prior purchases show up (If this works you can go back and turn off “Apps” under Automatic Downloads unless you want to keep that on). If not, try finding an app that you have downloaded before that isn’t currently on your phone (should have the cloud with arrow pointing down symbol next to it), download it, and then see if your prior purchases show up.