An IAS marked as lodged in QB but ATO hasn't received for some reason. Is there a way I can try to re-lodge via QB or any known reason why this would stop working?

There’s an error in setting up E-lodgement, @simone-tierney.

Our customers are unable to connect the QBO account to ATO for BAS lodgement and get an error: QuickBooks is not connected yet an application error has occurred while processing your request.

To constantly receive an update about this, you can be added to the email list by reaching out to our Customer Support team. Here’s how:

1. In your QuickBooks Online, click the Help menu in the upper-right corner.
2. On the Search tab, click an article and select Contact us at the bottom. Then, enter the details of your concern.
3. Click Let's talk and choose Chat or Get a callback.

Please check this article for our support hours: Get help with QuickBooks products and services.

As a workaround, you may consider lodging the BAS or IAS through the ATO Business Portal. 

Keep in touch if you still need help with your account. I'm always here to assist.