Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b0b10c9336779a1f6a1fecb546cf5c81.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563