QuickBooks automatically logging out in the middle of doing a task can be caused by a couple of technical issues, Roanne.
 
Since you've already exhausted all user-side troubleshooting steps, I'd suggest reaching out to our live support teams. One of our support agents will take a closer look at this to determine why you're automatically logged out when editing invoices.
 
Here's how to reach out to them:
 
- Click the Help menu in the upper-right-hand corner of QBO.
 
- Proceed to the Assistant tab.
 
- Type in "contact support" in the chat box and press Enter.
 
- Select Contact a human, then click Live Chat or Call me back.
 
- Type in a short description of your concern and click Continue.
 
- Choose between Callback or Chat.
 
 
Don't hesitate to visit us again if you need anything else.