An App ID with Identifier '' is not available. Please enter a different string

I had this problem, too. It turns out that the problem and solution are quite simple. When an Xcode user runs an app on a device using their free personal account, the Bundle ID is registered to the personal account. Then, when the user upgrades to a paid Apple Dev account and tries to create an App ID using that Bundle ID - the backend system thinks that Bundle ID has been taken.

Fill out the form here at this website: https://developer.apple.com/contact/submit/ under the "Certificates, Identifiers, Profilescategory”. I did this and the problem was solved in less than 12 hours. This was Apple’s emailed response: "When you install an app on a device from Xcode using your Personal Team, the Bundle ID is registered to that account. I have deleted the Bundle ID "com.AppVolks.Random-Ruby” so it can now be registered on your paid membership.”

Hope that helps!

In my case it wasn't letting me because I set bundle id in xcode project BEFORE creating online, so I changed temporarily in xcode, created online then changed back to normal in xcode.

For me, I was trying to create an app ID for an Enterprise app. The app ID had "xxx.ios.yyy" in it and it did not like the .ios. bit in the middle. As soon as I removed the ".ios" part I was able to successfully register it. This happened to me twice with two different app IDs of different length, and in each case, removing the ".ios" segment fixed the problem.

None of the above answers helped me, but I just found the solution.

For those who couldn't benefit from any of the above answers;

I have 2 different teams as you see.

I noticed that I did debug before with other team and Xcode automatically created an App ID in second team's developer account.

I opened https://developer.apple.com/ for second team's account and removed auto-created APP ID

Then worked fine

I am using Xcode 12.4. And I have been facing this issue with Free account. Now I added Bundle Id to my paid account. Went through above answers but no luck.

Following steps solved my issue. You may try once. thanks

Actual scenario so far I realized :

1. Main thing is when you build with Xcode then Bundle Id auto registered with account[free account]
2. Same Bundle Id is not working for new Paid account bcz of duplicacy
3. For free account it is not possible to remove app/Bundle Id from App Store Connect
4. So have to change Bundle Id for new Paid account.
5. If it was paid account then possible to remove Bundle Id from App Store Connect

Steps :

1. Sign with free account again on Xcode Team
2. Sync with Xcode which create provisioning profile to sync
3. Then change Bundle Id to com.domain.appnamefree and sync with free account again
4. That means apple auto registered with this Bundle Id for this free account
5. Once this change got applied, the real bundle id became free and available
6. Then delete the free account from Xcode account
7. Now add paid account to Xcode Team
8. Change Bundle Id to com.domain.appname
9. And sync again so that apple recognised this Bundle Id for this Paid account

Me also got the same issue.

In my case i already registerd with my free account. We can't delete that app bundle id from our free account.

So i changed bundle id not app name and again i tried it's working.