When I insert my Apple Fitness redeem code, it loads and doesn’t apply the additional 3 months.

I purchased an Apple Watch from Best Buy, an app promotion said if new user you get 3 months off for free. When I ordered from Best Buy, I was given a code to allow an additional 3 months in total 6 months apple fitness. The apple fitness app is not taking the code and I may need a new one to redeem the additional 3 months.

[Edited by Moderator]