Using app but invoices won't save so for me it's a waste of time The app is not the best seems clunky and slow to load etc. It's not phone as other apps work fine

This is not the impression we want you to experience when using QuickBooks Online (QBO) app, p-inett1.

Let's make sure we meet the QBO app requirements for Windows or Mac. If you have met the system requirements, let's try holding down the Shift key while clicking on the app icon (hold the key down until the app opens) to refresh. We can also reset the app data to refresh your app data. Here's how: 

1. Click Help on the navigation bar at the top.
2. Select Reset App Data.
3. Allow a moment for the process to complete, and then close the app.
4. Be sure to right-click the app and Run as Administrator when re-opening.

Then, try creating an invoice again. If the same thing happens, we can uninstall and reinstall the app by going to https://quickbooks.intuit.com/apps/. Scroll down to the Get the QuickBooks Mac or Windows App section, and click Free Download. Feel free to visit our Sales and customers page for more insights about managing your company's income and customers.

I'd like to know how you get on after trying the steps, as I want to ensure this is resolved for you. Just reply to this post and I'll get back to you. Take care always.