Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3bb43599c53b0d0a3e7a641df471658d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563