Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/584d3deb4a20a7c2a25afb0964c4513f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563