Hi Joe Rodden,
Can you add a default email address (generic company email that you have an inbox for) to your token that will be used if the AM or BDA is blank. You could test that pretty easily to see if it works or if that is the cause of your issue.
So my email is actually hardcoded onto it. It was working fine with the single token for Account Owner (assuming since that's always there) it stopped sending once I added the AM and BDA, which won't be on every account. So can confirm it stops actually sending once others are added in.