Having followed your instruction, the game installed via Matrix works absolutely fine. So it must be a Steam issue.

Thank you, I appreciate your expedient reply.
I shall give it a go.

Hello,
I hope this is the right place to ask for tech support, if not please direct me to the right place.

I am facing an issue wherein I purchased the RTW3 on release, on Matrix.com. It worked absolutely fine, I played it lots, and enjoyed it. However I allowed my copy to get quite out of date ...