I am attempting to send an email to a contact group in Civi (approx. 248 contacts) using the standard email - send now (to 700 or less) function. Once I set the sender and enter the email text, after hitting the send email button, I receive an error message blocking the send (screenshot attached).

. I double checked donor records from the group I was attempting to send to in order to confirm nothing was actually sent.

I first encountered this error yesterday at approximately 8:00 pm UTC. I tried refreshing Civi and restarted, but I am still receiving the same error today. It's a priority to send this today. Is it possible to investigate a fix?