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?

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?

Paypal Currency not pass corectly to paypal even if the currency has been filled from the Artio Book Paypal administration page because of the folling error

Path :/components/com_booking/views/payments/paypal/
File : button.php
Line #67

Wrong: <input type="hidden" name="currency_code" value="<?php $currency; ?>" />

Correct: <input type="hidden" name="currency_code" value="<?php echo $currency; ?>" />


P.S.
Also .. i suggest to put the following line...for other languages like..greek characters..

<input type="hidden" name="charset" value="utf-8" />

When the "Search - Booking" plugin is enabled
the search isn't working as it should..
producing the following error

Fatal error: Class 'AModel' not found in ../httpdocs/administrator/components/com_booking/defines.php on line 115