Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ccb1123ba9f0b1a0920f256561b9eb6d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563