Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bb9dccc0e91aec8cb25d7f7a1f5dd3ad.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563