In short: Open the Request → "Reject participation" → select a reason → confirm.
How it works
Open the Request via "Fill out request" in the email.
Select "Reject participation".
Select a reason for rejection and, if needed, add a message via "Add a message".
Confirm with "Reject participation".
Good to know
Your customer is notified automatically.
With "Undo rejection" you can withdraw the rejection and still respond to the Request.