OK, first, I don't know if you've read the threads pertaining to SAMs, but there are a few unexplained things about them. It seems that some people cannot run certain SAMs no matter what they do. We have yet to find a common point to lay the blame on. Even one of my testers had to place the FPK into CustomAssets for one map. It played fine for the other testers and myself. Odd, just on SAM for one person.
But, back to your problem. First, when you unzip a SAM, most of them contain two things, a folder and an FPK file. Don't open the folder and place the contents in UserMaps, place the whole folder in there. Your upload worked fine for me, but in your system, and possibly others, who knows. The best way to handle SAMs, in my opinion, is to keep the Zips in a folder somewhere. When you want to play one, copy the Zip to the EMPTY Usermaps folder, then unzip it in there. Don't extract the files from the folder contained in the Zip. 99.99% of the maps will be one click to the left when you get to the map selection page. I say 99.99% first to cover myself against lawsuits

and second because there is one little bugger of a SAM that seems to want to hide among the Original maps when I load it

. Second, do you use No-CD? (you don't have to answer that if you don't want to) One member, it seems, found that if he used the No-CD set-up that he couldn't run SAMs or CICs.
Try the download below and see if it makes a difference. Then the other thing, if it applies. Let me know what happens.
I'm correct 97% of the time..... who cares about the other 4%....