msdyncrmWorkflowTools Email To Team - Email sits at pending

Hi

I am trying to send an email to a team using the msdyncrmWorkflowTools Email To Team.  However the email sits at "This message has not yet been submitted for delivery. For more information, see help", and it sits at pending send. Another email created on the same workflow (Just sent to myself only) sends ok.  I am using Dynamics 365 online.

What do I need to do to make the msdyncrmWorkflowTools Email To Team email send?

Any help would be much appreciated.

Thanks