Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/935a9e1c9beee13a2de3a8e0372b9422.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563