The after signup email is a one-time email that is sent to contacts after they've signed up for your display. Typically, an after signup email isn't sending because it hasn't been properly enabled as they are disabled by default. 

Troubleshoot after signup emails

To ensure a display's after signup email is enabled: 

• Navigate to the Convert > All Displays via the main navigation. 
• Select the display in need of an after signup email. 
• Select the Follow-Up step in the display builder. 
• Enable the desired email(s) by switching the Published? toggle to the ON position. If the display is active, the email(s) will start sending to contacts who submit the display immediately. Make sure your content is customer-ready before taking this action.

Note: Enabling an after signup email on an active display will not retroactively send the email to contacts that have already signed up via the display.