That is a common problem with multiplayer sessions. After downloading the session (which you have done) you then need to clear the download box, select the session once more but this time select "view dependencies!". Assuming you have not already completed this step it will say there are a few missing ones..Select "view in main list" , scroll down and drag missing ones to download box and download them. Repeat this step to check that you have not missed any. The other thing that causes thaat message to appear is that one or more of the assets is locally modified. While looking for missing dependencies in the Main List have a look to see if any of the assets have a green triangle lit up. This indicates the asset is Locally Modified. There are a couple of ways to fix it. Deleting the offending item and re-downloading it should fix it. As does selecting it followed by the option "revert to original". Any further problems, just post here. I,ll be in the session later today and I look forward to seeing you in the game. There,s plenty of work for you, LOL!