Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/31054c76da79cc595f5f7b8f5bad1e24.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563