Hello there, @userchandleyph.
QuickBooks Online (QBO) works with multiple applications as long as it's listed and available on the app center. Let's verify if the Gas Engineer Software integrates with QBO. If not, I recommend reaching out to the app provider and request them to contact our Developer Team to initiate a connection between the application and QuickBooks.
Also, feel free to visit our Help articles page for reference. There, you can read some of the helpful articles that'll guide you in your future tasks.
We're always here to help. Your success with QuickBooks is our top priority.
Hello there, userchandleyph. I've seen the screenshot you've attached above.
I appreciate you for sharing the error message you're getting here. Have you tried replying here using a private browser? If not yet, let's try it to isolate if the error is caused by having too much data is our browser. Here are the things to do:
Please let me know if you still need assistance with this matter. I'm always free to help. Take care and have a good one!