Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d5015e4e3d4d9a1916c3c0c0fccad73d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563