Hi BradW1,
If you're trying to get the invoice to open properly for the person receiving it, the best workaround is to update the logo used on your invoice template.
A large or high-resolution logo can cause the PDF to come through blank or with red lines instead of the invoice details. To fix this, open Sales settings > Templates, remove the current logo, then email a test invoice to yourself. After that, upload a smaller or lower-resolution copy of the logo and send another test.
If needed, create a fresh copy of the logo first by taking a new screenshot or snip of it, save it as a PNG or JPG, then upload that version to the template. If the test invoice opens properly after that, your customers should be able to see the full invoice details again.
Regards,
Genreve