Hello there, @zemboe.

Allow me to step in and help share some insights about importing custom template.

If there are issues with the mapping it will download instead of receiving the preview. You should be able to preview and confirm your style if it matches the QuickBooks field. Let's try uploading the sample file provided in QuickBooks to check if you keep having this issue.

However, if you still can't preview using the sample template, I'd suggest contacting our Online Care Support to check this further. We've recently updated our support experience and the best way to reach them is to select the Help icon on the top right of your account and click the Contact Us at the bottom of the panel. 

Please reach out to the Community again if you have other questions about importing custom template. I'm here to help however I can.