The ‘Profit & loss’ section of the app doesn’t show me any data at all?

I can help you with resolving the error you've encountered to generate the report that you need, @joel-uden-conten.

First, try to check if you're only having this error using the mobile app. You can run your Profit and Loss report through the web. Here's how:

1. Open a web browser and go to this link: http://qbo.intuit.com/. 
2. Go to the Reports menu and look for the Profit and Loss report. 
3. Set the report period and other customization.
4. Click on Run report.

If you have transactions on this one, then I suggest resetting your QuickBooks Online (QBO) app to its default state. It's possible that piled-up cache in your application caused this unusual behaviour.

To resolve this, you can hit the Clear Data option in the Storage section of your mobile phone to reset the app to its default state.

Here's how to clear app cache or data storage if you're using an android:

1. Open your phone's Settings app.
2. Tap Apps & notifications and click on See all apps the app Storage.
3. Select Clear storage or Clear cache. If you don't see "Clear storage," tap Clear data.

For IOS:

1. Open Settings and swipe down and tap Safari.
2. Swipe down again and select Clear History and Website Data, click it once again to confirm.

If you get the same result, you can check out this article to solve the common error in the mobile application: Common Errors in the Mobile App.

In case you'd encounter any errors between the Profit & Loss and a Sales reports, the following article will help you fix it: Profit and Loss report does not match a sales report.

Let me know if you need further help in generating your reports. I'm always here ready to answer them for you. Take care and have a great rest of the day!