Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/4f770b676c1e0d5c266a05c94ddda568.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563