Journey Test Mode throwing error

Hi Team, 

I was creating email content from journey optimizer and while i try to do a test mode , I am getting the error in test mode and the error is as below-

"The message has not been published" and the error code that i see in the log is -  CJMCMP-2202-400

So not sure if there is any issue with the email body or the email channel as such, as i do not see any alert shown in the email body. 

And also do not see where to publish the message apart from saving the email body / content. 

Requesting for any help in here. 

Thanks,
Adithya