An App ID with Identifier 'com.example.app.extention' is not available. Please enter a different string

Version 7.3 (7D175)

The Application ID Name should be same as application bundle identifier, if you application bundle identifier is com.abc.xyz than the application ID name for this bundle ID should be XC com abc xyz

A name in any other format won't be seen by Xcode.

If your application is already on app store and you are submitting update than just change the app ID name accourding to above formate and it will work

I found the solution from Apple developer forums.

Apple has just updated their Dev Center CGU. It seems that the app extension bundleId is stricter.

if your app bundleId format is : com.my.app

your app extension bundleId now have to be : com.my.app.XXX

Creating new appID and provisioning profile fix the issue.

Check this link https://forums.developer.apple.com/thread/15712

Xcode to 7.3

I have encountered this issue when archiving and in my case, downloading all provisioning profiles on preferences cant fix this so I update it.

Try to check your app's Provisioning Profile on Member Center.

Go to Developer > Certificate, IDs & Profiles > Provisioning Profiles > All

Look for your app's Development and Distribution Profile, check if status is Invalid then Edit,

Modify your profile contents and select the Generate button to save changes

Finally, Go to Xcode> Preferences > [Apple account] > View Details and Download All to refresh your provisioning profiles

Clean. Build. Archive. Success ! Hope it helps :)