Apple Developer Portal adding UDID: 'invalid or already registered'

Question

I attempted to add a device UDID to the Apple Developer Portal(copy-pasted from iTunes device summary), but I received this error:

"The following devices are either already present and were not modified or contain invalid identifiers"

The UDID has never been added before, and it is identical to the UDID visible in the Xcode devices view as well as the iTunes device summary, so I believe this error is invalid.

A family member gave me this older iPad2, (running iOS9.3.5) that I'm trying to add the UDID for. She purchased it directly from Apple. It is not jailbroken or altered in any way. (Including this statement to reassure the reader that I'm 100% positive nothing has been altered.) I have added many devices to the portal in the past, and never encountered this issue. Not even sure where to begin to solve this. I filed a bug report with Apple.

Answer 1

Disable it in devices list, than managed to register with Xcode again

Answer 2

It may just say that, allthough it registers fine. Check again.

Answer 3

I also encountered the same issue, but I found that I made a mistake. In my case, there was a same UDID in the device list. Try to check this first.

Answer 4

This can happen if you're importing bulk devices via csv import, and the file is plain ascii. The fix is to recreate the file with a UTF-8 BOM added to the first line (see here)

Answer 5

Another reason for this would be if the last column is not 'ios' or 'mac' (when importing via csv files)