This article will go through the step-by-step process of what happens from a manager's point of view when an employee declines a shift. For an employee to be able to decline a shift, you need to give them access first (see here for details).
When the employee clicks Decline, an email will be sent to the manager. For a manager to be notified of a declined shift, they need to have notifications turned on. Alternatively, they can log into the roster to view any unassigned shifts as when an employee declines a shift, it reverts to being unassigned.
The below example is an email received by a manager (who has notifications turned on) after an employee has declined a shift. A manager will be notified via email (below) when an employee declines a shift. They will not be notified via SMS.