Hello there, @imperialplumbing.
I'm here to guide you on how to troubleshoot this issue with the integration. I'd like to know if you've encountered any error message when you try to connect with QuickBooks using your Gas Engineer Software App.
If there's an error message, you may check out this article from their website to do the task: Quickbooks Integration with Gas Engineer Software. If there isn't, you can contact their support team to help you further what has caused this issue.
I'll be here if you need further assistance. Let me know in the comment section. Have a good one.
