Thanks for getting back to us, @concrate1.

I realize you're devoting a lot of time and effort to finding a solution to your problem. This isn’t the kind of impression we want you to have. Rest assured, I’m here to provide updates on this concern about the invoice email delivery issue.

Currently, we received reports that some users are having the same issue with being unable to send invoice reminders. I suggest reaching out to our Contact Support Team. This way, they'll add you to the list of affected users and notify you via email for updates.

In the meantime, you can read through this article for more details about invoice reminders: Send invoice reminders automatically or manually in QuickBooks Online.

Please feel free to get in touch with me here for any additional questions about managing your invoices in QuickBooks Online. The Community always has your back. Thanks for dropping by and stay safe.