I was also having issues. Things were working fine until I added extra users so I could email receipts from different email addresses. Then for some reason tracking stopped.

Try to "manually" track a trip. Don't worry about exact input numbers when prompted. Add in anything. The point is to get the app manually tracking. I found that once I did this the app started tracking automatically again.

Also make sure you are logging in with the original user/pass you set up as opposed to logging in with a 2nd users credential if you've set up multiple users.