Hi there, @Kamper12.
Currently, we have an ongoing investigation (INV-78254) about invoice delivery issues in QuickBooks Online. Rest assured that our engineers are working on a fix.
I recommend contacting our Customer Care Support team so that you'll be added to the list of affected users. This way, you'll receive email updates of the investigation's status and be notified once it's been resolved. I've included the steps to contact support below.
- Click the (?) Help icon in the upper right-hand corner of the dashboard.
- Select Talk to a Human.
- Enter a short description of your concern and press Enter.
- Click I still need a human.
- Select Contact Us to connect with our live support.
- Choose Get a callback.
In the meantime, you can send the invoice manually by selecting Print/Preview, downloading the PDF, and sending it via your own email.
I appreciate your patience as we work through this. If you have any other concerns, please don't hesitate to drop a comment below. Take care, @Kamper12.