When you add a volunteer to the Shift using the "Add New Volunteer" button from the Shift details screen on the V4S Kiosk application, you see the message as volunteer added successfully.
But the volunteer is only created as Contact in Salesforce, and not signed up and added as a volunteer to the Shift.
This is happening because the desired number of volunteers for the shift you added the new volunteer is set as 0 or blank in Salesforce.
Please make sure that the Shifts are created with the desired number of volunteers in Salesforce.
If the desired number of volunteers is 0 for a Shift, and you try to add a new contact and also to be signed up as a volunteer using the "Add New Volunteer" button that is on the Shift details screen, then that contact is only created as Contact in Salesforce and not Signed up as a volunteer to the Shift.
The desired number of volunteer is blank in Salesforce
Add volunteer to the Shift using the Add New Volunteer button in the V4S Kiosk app.
