SOLVED! Happen to be running windows v0.19.1 myself also (got it couple of days ago), not sure did "plugins" directory exist before first run or before trying to install first mods, but as far as i seem to be able to observe and understand not single plugin part of any mod tested this far seems to load. I am currently trying to use: Subassembly loader (does not cause that icon to appear in assembly building) MechJeb 2.0.7 (that single part it adds appears to menus and i can add it to crafts, but it does not do anything [other that make game think its command module even while its not in command modules tab], but dont have any extra windows) Lazor cam v26 (in this case not even part appearing, nothing even pointing to mod being installed) Kerbal attachment systems 0.2.3 [this one was marked expecially as 0.19.1 mod] (parts appear in menus, can add them to crafts, but they dont do anything, when rightclicked while controlling craft nothing happens [no menu] and when eva with kerbal nothing still happens when standing next to them) Have files that were in "plugins" directory in mod packs in "plugins" directory in kerbal space program root directory, have my kps in random non operating system directory (c:\games\kerbal space program) ... hmm now coming to my mind could it have some problem loading some of stuff from path where there is long directory names or something, extremely rare these days but still have seen in some games... have to test that.. SOLVED! Reason was firewall partially limiting ksp, didnt think of looking since singleplayer at this phase of gamedev.