Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/6d40fb1a68f32789c7dce47791c2528d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563