Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3c62e6b1ca40b3d4558a68c84985a8f0.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563