Welcome, lucasgozzard.  :)
Is it possible that you are mixing up the definition of ZFW? This would lead you to wrong numbers and the FMC to define those wrong values as invalid entries then.
The ZFW is your empty weight + passenger and payload (usually summarized as "payload" in FSX).

Maybe this tutorial can help you too. http://www.captainsim.org/yabb2/YaBB.pl?num=1220997876