Hello there, @ Mr Mark.

Thank you for reaching out to the Community. I understand how important to print your invoices in your QuickBooks Online.

Upon checking here on my end, there’s an ongoing investigation about printing invoices. Rest assured, our engineers are aware of this and they’re doing their best to find a solution to fix it.

Thus, I encourage you to contact our Phone support team. They can add you to our notification list and you'll be notified via email once the update is available.

Moreover, I'm adding these helpful articles on how to customize your invoices and receive payments in QBO:

Customize invoices, estimates, and sales receipts in QuickBooks Online

Record invoice payments in QuickBooks Online

Feel free to post here again if you have more questions about printing invoices and other QuickBooks-related concerns. I'm here to lend a helping hand.