Why won't quickbooks allow me to add a third vehicle to my business?

Welcome to the Community space, Kassy.

Let me provide you with troubleshooting steps to fix your issue when adding a third vehicle in QuickBooks Online (QBO).

If you're using a web browser, there's a possibility that the browser you're using has data issues that cause QBO to act weirdly. Let's log in to your QBO account using a private browser. To do this, follow the shortcut keys on your keyboard:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Safari: Command + Option + P

If this works, you'll need to clear the browser's cache so the system can start fresh. If the issue persists, I suggest switching to a different supported browser.

On the other hand, if you're using an IOS device, you can follow these steps: 

1. Go to the Settings app.
2. Tap General, then iPhone Storage.
3. From the iPhone Storage screen, tap the QuickBooks Online app.
4. Select Offload App.

After refreshing, consider restarting your mobile phone, then check if you can add a third vehicle. If you encounter the same issue, proceed to uninstall and reinstall your QuickBooks App.

If you're using an Android device, let's do some troubleshooting to fix it by following the steps below:

1. Select the menu at the top right and choose Settings. 
2. Press Refresh Data and choose Yes.

Moreover, I'm adding this article as your reference in tracking your mileage automatically in QuickBooks Online: Automatically track mileage in QuickBooks Online.

Return to this post if you have other concerns about adding a vehicle and other QBO-related issues. I'll be here to lend a hand at any time.