Deleted

Weird

It ended, so I can't check if I am able to join.but this is the base game> here

Assuming that "doesn't own base game" was the message people got, my guess is that there's something broken with the API and it's reporting a different ID as the basegame. I;m too lazy to verify it, though.

Since SG won't let users enter for DLCs unless they show as owning the base game, certain steam configurations can cause that kind of entry restriction.

In this case, Retribution is configured by way of a lot of internal DLCs [>>], which may indicate that Dark Angels and similar packs are nested DLCs (that is, a DLC of a DLC) of those components. As SG can't check DLC ownership [and thus can't apply it for base game ownership checks], in situations like that you end up not being able to be recognized as owning the base game.

Steamdb.info sheds light in this case:
it shows there is a specific app that is required as owned to purchase this DLC:

MustOwnAppToPurchase - Warhammer 40,000: Dawn of War II - Retribution - Campaign DLC (56437)

Unfortunately this itself is a DLC (which is included in every package that contains the proper base game). I say unfortunately because most DLC are not reported properly as owned by the Steam API and this seems to be the case here.

(Basically what Sooth said...)