Failure to Send error on Recipient Time Zone email

Hiya Nation!

We just got the new update that includes recipient time zone send (yay!) however, when trying to send out an email using it, the email failed to send.

I wasn't able to get a screenshot of the notification, but it basically said the message was unable to be sent. I did clone the program from a previous one but I've done that many times before to send a new email. I was sure to have the time set to 30 hours in the future (for both recipient time zone and headstart) and refreshed the smart list members.The issue still occurred.

Any ideas on what might have caused it? I really want to be able to use Recipient Time Zone as it's a feature I've been waiting for since our migration!

Thanks!