Let's fix it together, DebC-TSB.

The QuickBooks File Doctor is a tool that determines and fixes any errors on your company file. We can run this so we can resolve the email issue. In addition, let's make sure that we successfully set up folder and Windows access permissions. This can also be the reason why you're unable to send the invoices in multi-user mode.

Also, let's check your QuickBooks Database Server Manager (QDSM) if it's updated. Any error with QDSM can also prevent the other users to send invoices in Multi-User mode.

You'll want to temporarily send the invoices via single-user mode if the same thing happens. Then, please reach out to our Technical Support so they can check the reason for this. Simply go to Help > QuickBooks Desktop Help > click Contact us.

Comment below if you have more questions. I'll be here to assist you.