"An App ID with bundle identifier X is not available. Please enter a different string" (Xcode 7.3)

I just installed Xcode 7.2.1 and could successfully export AdHoc build with it. While Xcode 7.3 keeps on telling that there is something wrong with bundle identifier.

UPDATE:

Looks like changing the "Name" (not the ID) of App ID in developer portal under "Certificates, Identifiers & Profiles" to the next format "XC com mycompany appname" (in case your app ID was com.mycompany.appname) helps Xcode see your appID. Strange but it's working.

I also encountered the same problem. Xcode7.3

Effective solution is：

OK - I may have a solution. Though you won't like it because it is a major pain. I went to Apple members center, deleted all of my certs all of my profiles and started from scratch.

I wish I had solid steps to give you to follow but I did so much that I'd honestly just be guessing. In the end here is what I'd suggest:

1. Revoke all certificates
2. Delete all provisioning profiles; both in the member center and on your computer.
3. Create new certificates
4. Create new provisioning profiles using new certs.

I'm now able to create adhoc builds and export them using xcode 7.3.

All of that said, do this with the intention to get into some BS. It took me a long time to get things set up and working again. From re-creating all of the above to countless device, xcode, and computer restarts.

Now a new issue has come up - dyld: Library not loaded: @rpath/ regarding one of my swift cocoapods ... so more fun. What a wasted day :(