My app got rejected for the following reason but I'm not using the advertising identifier. Used the following command
find . | grep -v .svn | grep "\.a" | grep -v "\.app" | xargs grep advertisingIdentifier
and got "Binary file ./libGoogleAnalyticsServices.a matches" as a result.
More details on the rejection
PLA 3.3.12
We found your app uses the iOS Advertising Identifier but does not include ad functionality. This does not comply with the terms of the iOS Developer Program License Agreement, as required by the App Store Review Guidelines.
Specifically, section 3.3.12 of the iOS Developer Program License Agreement states:
"You and Your Applications (and any third party with whom you have contracted to serve advertising) may us the Advertising Identifier, and any information obtained through the use of the Advertising Identifier, only for the purpose of serving advertising. If a user resets the Advertising Identifier, then You agree not to combine, correlate, link or otherwise associate, either directly or indirectly, the prior Advertising Identifier and any derived information with the reset Advertising Identifier."
Please remove the iOS Advertising Identifier from your app or add ad functionality to your app.