I think this has been downrated a bit for technical issues. My guess (see discussion thread) is that the author playtested this using the rerelease gamedata; the QuakeC differences there could explain some of the broken trigger behavior other folks are seeing. Not an unreasonable thing for a new mapper to do so I won't ding it for that.
Anyway yeah to play this, it seems like you could use the rerelease gamedata. Or, since the QuakeC changes in the Copper mod have some of the same fixes/changes to trigger behavior, using Copper as a base mod also reportedly does the trick.
It's a bit of a shame that the early discussion was so much about the tech issues, because this is a fun little "first map"... bundling in some tricks, "special effects", and cool moments. I like the energy!