Frozen Kindle App

My Kindle app freezes immediately after I open it. I have tried a hard reboot, deleting and reloading the app, and turning on/off whisper sync. The app is synced to my iPhone, where it appears to work. This is a chronic problem that constantly reappears. Now, as a result of all the deletes and reloads, I have started to lose highlights and notes from old books. Please help.