Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/55e3c5b84fda6018ab9b81b5e60a924d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563