Some of my categories have disappeared, then they reappeared for a day and now they have gone again. I have not changed any settings

I understand the urgency of resolving this, Claire. Let me provide troubleshooting steps and a workaround to help you categorize your transactions.

Since you've mentioned that your categories disappeared as you use the QuickBooks Mobile app, I recommend performing these troubleshooting steps first:

For Android users:

1. Go to Menu ☰, then tap More Options ⋮
2. Select Settings, then Refresh Data.
3. Click YES to confirm.
4. Uninstall and reinstall the app if needed.

For iOS devices:

1. Tap the Menu ☰ and click the Help & Feedback.
2. Click the Refresh Data.
3. To confirm, click Refresh.
4. Uninstall and reinstall the app if needed.

If the issue persists and you're using an iOS device, I suggest contacting our support team since I found an ongoing investigation related to this concern. By contacting our representative, they can add you as one of the affected users, and you'll receive updates on the progress of the investigation.

Please know that our product engineers are fully aware of this issue and are working to resolve it. I appreciate your understanding as we work to address this matter.

Here's how:

1. In your QBO account, select Help (?).
2. Choose the Search tab.
3. At the bottom of your screen, click Contact Us.  
4. Type your concern. Then click Continue.
5. You can choose to Callback, Appointment, or Chat to connect with us.
6. Kindly fill out the provided fields, such as your First name, Last name, Email address, and Phone number.
7. Depending on what you choose as your way to connect with us, click Callback, Schedule an appointment, or Chat.

As a workaround, you can log in and categorize your transactions in any available web browser you have. You can also use your PC/Laptop at this moment.

To learn more about the available hours of our support, you can see this article:  QuickBooks Online Support.

After categorizing, and when you're ready to reconcile, you can use this article: Reconcile an account in QuickBooks Online.

We're still here to provide the necessary assistance whenever you need us. Just let us know by posting here in the Community forum or leaving your concerns in the comment section.