When the mission loads, the little cutscene plays and I am given a "Report In" task which seems to point to two sentries sitting atop a garage-like structure embedded in a hill. The task marker itself, however, seems to be underground (somewhere inside the garage, which is not accessible), and therefore the mission cannot begin. I don't seem to see any important characters like Stavrou or the British fellow.

An error message also pops up, which is shown in the screenshot. {F27785}