Hello,
I've been having this problem for a couple days now. When I open my Garmin Connect app it tries to sync and immediately crashes. I have tried all the fixes I have been able to find (reinstalling, changing permissions, deleting activities from the watch, installing previous app versions....) nothing has worked. I reset the default settings on the watch, and the app did start to work briefly, then however it started doing the same thing. Very frustrating, as I paid over $800 for this watch, and really it can't do anything without the app. Please help! I am using Android, and have a Forerunner 945