The Fitbit Community is a gathering place for real people who wish to exchange ideas, solutions, tips, techniques, and insight about the Fitbit products and services they love. By joining our Community, you agree to uphold these guidelines, so please take a moment to look them over.
I seem to remember that you have to set your profile settings (weight etc) along with your weight plan to be the same in fitbit and MFP. Might be worth checking.