Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/84d20e99e2f3667e74b9e20f1fee4c9d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563