Hi @123146175004559,

Thank you for bringing this issue to our attention. 

We have an open investigation for this specific issue. With that said, I suggest you contact our Technical Support team for assistance. They can add you to the list of our affected users. You'll then receive an email notification whenever an update becomes available. 

Take a look at this article for the steps: QuickBooks Online Support. 

Other than importing a custom template for invoices, you also have the option to add custom fields. See this article for the steps: How to add custom fields to invoices. 

Post a reply if you have other concerns with custom templates in QuickBooks Online, and I'll handle them for you.