Hi,
I do not know which version your friends got but the DLC is
standard included in the Digital Deluxe version, so on this version
it did not require a pre-order.
Right click BF4 on your Origin client and choose "show game details".
Scroll down to expansion. If China Rising was activated it should not
be greyed out. If it is I suggest you contact a game advisor to check
your account.
To contact a game advisor, go to
https://help.ea.com/en/contact-us/ask
* Fill in "account" in the search bar
* hit find solutions
* Then select product in the first selecting bar, account management in the second and select your platform in the last bar.
* Hit find solutions.
Now you will be given multiple solutions to your problem. To contact support you need to click "I still need help".
Here you can choose a contact option.