mileage app not logging miles.

I have the app permamently on because it's easier to delete trips not done, since I mainly  use my car for business. However it is not recording miles - Just puts random mileage in. Thinking of going to Xero as recommended  by a friend (who works in accounting) and she told me not to touch QBSE with a bargepole as it is notoriously difficult to use. Any ideas? Thank you.