Made for Email Saved as Site Template Does Not Allow "Send this news post as an email"

I have a site owner that created a template from one of the Made for Email templates for news posts. They have been using the template for a while and it has worked perfectly until today. When they attempted to "Send this news post as an email" an error messaged popped up and said, "Failed to send email." 

I cannot find any Microsoft documentation on creating a template from one of the Made for Email templates and I can't understand why it worked previously?