Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/db6d2d74058f295d70c50d8219180c6d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563