Hello john306,
Welcome to the Community. It's important mileage tracking is working so you can continue to manage your work with peace of mind using QuickBooks.
In order to successfully track the mileage, you'll need to have the app running in the background. I recommend checking to see you have the app running while traveling your your return trip. I also recommend troubleshooting this issue using the following article that shows you how to: Fix mileage tracking issues in the QuickBooks Online mobile app.
Let me know if you have other questions. I'll be a message away.
