Appointments+ Confirmation Emails Not Sending


I am having a little bit of a meltdown here and am looking for some serious help!

I have the system setup to send confirmation emails upon payment. I understand that PayPal has to send an IPN to my site to confirm that payment has been received. I have taken the IPN link provided in the settings section of Appointment+ and added that to my PayPal account IPN settings section.

I have conducted a test purchase in the Sandbox but:
A: No confirmation mail is sent.
B: The appointment made is not automatically set as confirmed.

Please can someone just point me in the right direction to resolve this issue.

Thanks a bunch!