Did you put it in Plugins or Plugins\FX? It should be put in the former, and overwrite the already-existing file with the same name. If you renamed the old file, be sure it doesn't appear anywhere where Reaper could find it, or it may use the original control surface plugin instead of mine.
In other words, it's not a VST/DX/JS/whatever plugin, it's a Reaper native plugin. It should replace the original control surface driver (the one with Mackie, Faderport etc. but without US-428).
Once it's finished, I may try to post it to plugin developers forum and ask if it could be integrated into Reaper - it would be best to have US-428 support "out of the box"
