Enable asking to send crash report once answered with No

One of my app users had a crash when starting the app. The first time when he was asked "Send Crash Report?", he answered No. Now it's almost impossible to get to information about the bug, because after new crashes (now every time when he tries to start the app), he isn't asked again whether he want's to send a report. Is there a way to somehow reset his "No" answer so he gets asked again? He already tried: * delete cache of the app * force close the app * restart the phone * delete cache of Google Play app Note: I don't have something like Crashlytics or ACRA in the app. Only plain default reports to Google Play, which worked quite well so far. User's phone has Android 5.1 installed.