That's a bit odd:
- how do you know it fails to update? Have you compared the version numbers, of the running version and the version you downloaded?
- are you expecting a firmware update to change the configuration (close ports)? That assumes the update resets the router to defaults, which might not be the case.
- Can't you just close the ports you want closed? I agree that you wouldn't want any open unless you were running a server behind it.