Let me provide some update on this issue, @rob123.
The issue in which customers are not able to view sent invoices is already closed. And we've got an update from our product engineers that can help fix the current concern of yours.
You can consider resending the affected invoices or send a reminder to your customers. This way, they can view the invoice PDF on their end. To do so, please follow the steps below:
- Sign in to your QuickBooks Self-Employed account.
- Click Invoices from the left menu.
- Find the invoices you want to resend, then select Send reminder under the drop-down beside Mark as paid.

As always, feel free to visit our QuickBooks Community help website if you need tips and related articles in the future.
Please post a reply below if you have other concerns with your transactions in QuickBooks Self-Employed. I'll be more than happy to assist you again. Have a great day and take care always.