Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/933e5a8eb5f41571d1c41425a3a5a9c2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563