Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/433c2d1a95c6616ab50e2a54440f6f9a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563