Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f9db4a81c21d36aac6af8c107daa1d52.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563