OK I tried it. All works fine for me. This is a single mission. To install it first unzip the downloaded file to a Temp folder. You should have something like this.

Paste the Abatros_D_V & SOPWITH CAMEL F1 BLUE BARON folders into CFS2\AIRCRAFT. Open the MISSION folder & paste the included Camel Trophy .mis file into CFS2\MISSIONS. Now fire up CFS2. The new mission should be listed under the Single Missions/British menu as Camel Trophy. Britain is included in the default Country.cfg so this does not need modifying unless you wish to use updated splash screens..
The only reasons I can think of for it not working are
1. You didn't install the files correctly
2. You're missing the default A6M2_ZERO. This is important as the sound of the 2 included aircraft is aliased to it.