Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b40985fead3a4f04e8a76c2a1370d7f3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563