Using S-Function Builder with xPC Target

I used the S-function builder to compile some C-files that I used in Simulink. However, when I went to run it in xPC Target, it built correctly, but then when I attempted to connect, I received an error message stating "External Mode Open Protocol Connect command failed" and that the model on my target and host were mismatched.

I've been searching for documentation on how to use the S-function builder -- or at least code produced by the S-function builder -- with xPC Target, but all I've found is guidelines on building S-functions and questions regarding peoples' issues with their own, specific, C-code problems. Is there any better documentation on how to adapt an S-function put together with the builder to a form that works on xPC Target?