Hi there, @Fafa24.

Delighted to have you here in the Community. I'm here to help you with determining why the borders are not showing when printing invoice in QuickBooks.

The Do not print lines around each field in the printer setup preferences might have been checked and causing this issue. To fix this, you'll need to change the printer setup preferences.

Here's how:

1. Go to the File menu at the top, then choose Printer Setup on the drop-down.
2. From the Form Name drop-down, select Invoice.
3. In the Print On area, select Blank Paper.
4. Uncheck Do not print lines around each field, then select OK.

You can check out this article for more information: Troubleshoot common issues when using and customizing templates.

That should get you fixed right up! I also attached some screenshot for your reference.

Thanks for being a part of our QuickBooks family. Please let me know if I can provide some additional assistance. Enjoy the rest of the week.