In the wind load commands for your model, the type number referred to is 1. Take the following statement for instance.
WIND LOAD X 1.7 TYPE 1 XR 0 58 YR 0 15 ZR 0 8 OPEN
Under your DEFINE WIND LOAD command, do you have a type number 1? Here is a sample data set to illustrate what I am talking about.
DEFINE WIND LOAD
TYPE 1
INTENSITY 80 HEIGHT 50
In the above set, notice how I have used a type number 1.
If the TYPE numbers in your model start from 2, that can trigger the message you encountered.
Attached is a simple model in which the wind load command is similar to what you have. Try opening it and check if you encounter any errors.
If you are unable to solve it on your own, please attach your STAAD input file, and I'll take a look.