Got fastdl? If so you'll need to update the lua cache
It would say in big red letters of doom at the top right corner it's not being downloaded.
(Also, about scriptenforcer, my game automatically freezes sv_scriptenforcer at 0 when I join. I don't recommend only using that as an anti-cheat.)
Polish, install the latest svn version of ulx and ulib. The download on the website is always outdated.
And if that doesn't work, go to your server.cfg file and add
sv_downloadurl ""
sv_allowdownload 1
Restart, then see if it works.