How can I fix the invoice delivery issue that affects all my invoices?It has nothing to do with settings or addresses being incorrect.

We appreciate you letting us know that the email address is correct, info2181.

Before we proceed, have you cleared your browser's cache and cookies? If not, please do so, as browser-related issues can affect functionality. On top of that, configure your server to accept QuickBooks Online's mail server hostnames and IP addresses. With this, consult an IT expert for assistance.  

Alternatively, if the issue persists, contact our live support team directly. They have the resources to examine the cause of why you're currently experiencing this matter.

For now, consider downloading the invoice as a PDF and sending it manually.

Here's an article you can refer to learn about processing invoice payments: Record invoice payments in QuickBooks Online. 

You can hit the Reply button below if you have more questions about sending invoices.

I am having the same issue and have had for a few months now. I seem to be able to send from an incognito tab (thought not always) and from my ipad. However, last month I did this and they STILL were not sent and none of my customers have paid me as they did not get the invoice - they all pay exactly on time so it's clear they are lacking the invoice. Quickbooks has just raised the cost for their service whilst reducing the ability to get paid - which does not make sense. It also doesn't make sense that you're supposed to clear cache/use incognito to send an invoice. Just stupid. It's worked for years - please fix this immediately. It's a fundamental requirement for a small business accounting solution - the ability to bill. I have been sending invoices to these customers with same email addresses for years - that is not the issue.