Advertising Identifier declaration missing? Testflight external testers

Hi all,

i've tried to submit my app to the beta review (testflight, external testers) and got this mail after submitting.

Undeclared Use of Advertising Identifier [IDFA]. Your app contains the Advertising Identifier [IDFA] API but you have not indicated its usage on the Prepare for Submission page in iTunes Connect. Click Submit for Review to access the Prepare for Submission page and indicate IDFA usage.

After this the word "invalid" appears beside the upload date in the build section. At the submission process I wasn't able to declare the IDFA, because there were only the cryptography questions. I did this twice now...

What can I do to fix this issue?

Best regards Dennis