Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/280c21bb07a4b621d90ae7a1deaaf865.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563