In Xcode 6 (at least 6.1 I am using now)when you are doing the export for ad hoc, xcode 6 will automatically scan if there is any provisioning profile contains all devices registered in the developer account and at the same time match the bundle ID. If no, it will use XC provision profile. Therefore, if you want to use your own profile, for example, for the purpose of push notification, you will need to select all devices in your profile on apple developer portal. I guess that's the reason why some people recreate profile would work and some wouldn't.
btw,use script can export and upload to testflight, but device just can't download it. probably somewhere I got wrong. if anyone knows why it is, pls let me know. tks