Have all your emails been created and tested?
Are you using the correct sender name, address and subject lines ?
Are the correct emails linked to the correct email actions in the campaign journey? Pay particular attention to this one - it's not uncommon to accidentally link the wrong email to an email action, especially if you create the emails after you've created the journey.
We want email 2 to go out.
But email 1 has been defaulted in the email selector.
We can then change this to email 2 to ensure the correct email is sent out.