When i use paypal payment and complete the paypal payment procedure successfully
when i click return to the site..the system redirects to the frontpage
and the reservation Paid Status remains to "Unpaid"

Can you reproduce the problem?

PS1.
I filled the "Code" (Unique identify code) with the paypal' s "Secure Merchant Account ID"
is this correct?

PS2. This code..is not used anywhere in the code as far as i can see...is that for future implementation of some ipn perhaps?

After many hours of investication...i come up that the problem is that
the $response from the paypal is INVALID!!!

The problem is in the controller

path : /components/com_booking/views/payments/paypal
file : controller.php
line : #64


PS1.
I use sandbox and i have tryed with ipn enabled and disabled...
if the correct is enabled what should be the path?

PS2
And..if its not..how...would the module...notified by the paypal when i accept the payment?

Thanks for your notice. We will test it.