Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7a6061b20c38f4ea88b38d8de455924a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563