I'm running the latest Stable Build (0.72) and it works fine for me, tried it a couple times and both times OpFor showed up pretty quickly after I got the First Phase completed msg. Also, played this one online a lot and there has never been a problem with OpFor not showing during the sessions I was a part of. If you've already tried it after disabling your mods, I'd try redownloading?
Edit: Ah, your running it in dev that may well be the problem - I've never had a problem with it in Dev but haven't played it with the latest couple builds (at least), I only reverted to stable last night, so it's working fine with the latest stable build if that's an option for you?
