This map requires you have Half-Life 2: Episode 2 installed and mounted in order to see all of the materials and models used in this map. The coniferous trees, terrain textures, and particle effects all use Episode 2 content, to name just a few!

http://psteamproxy.yuanyoumao.com/app/420/HalfLife_2_Episode_Two/

Please ensure these requirements have been met before troubleshooting further.