Check to see if a payment page is used instead of proceeding directly to payment on the form:

1. Edit the form
2. Scroll to Payment Options.
3. If a payment page is selected, browse to that page and edit the Payment part.
4. Make sure that the radio button is selected to 'Send the acknowledgement email defined for Donations, Event Registrations, Memberships or eCards that use this payment part'.
5. Click Save.