Hi,
BFBC2 Deluxe Edition DOES contain the Vietnam DLC. It would not be DE otherwise and it is even listed on the Origin page. Normally when getting it on Origin the DLC is linked to you account and you would only have to login to your Origin account ingame. The game would see you have the DLC attached to your account and will not ask for a key. As this is code related I suggest you contact a game advisor.
To contact a game advisor, please visit the following site:
EA Help - Contact Us
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You will now be provided with the contact options that are available, depending on your country.
With best regards,
inSmithereens
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