Welcome to the QuickBooks Community! Thanks for reaching out to us here. This is currently a known issue within QuickBooks. Our engineers are working hard to get this fixed in a timely manner. You can use this link to subscribe to updates regarding the issue. In the meantime, you can:
Select the invoice and go to View/ Edit
Go to the bottom of the invoice and select Print/ Preview
Select Download
Then send the download via your email
If you have any other questions, feel free to reach back out to us.