Lost my AoE2 HD DLCs – Steam says I already own them but they don’t show up in game

Hey everyone,
I’ve got a weird problem with Age of Empires II HD. I bought a few DLCs about a year or two ago and they used to work perfectly. Now they’re just… gone.

When I try to buy them again, Steam tells me I already own them — but in the game they don’t appear anymore.

The only thing that might matter is that I don’t actually own the base game myself; I play it through Steam Family Sharing. But the strange thing is, this setup used to work fine — I could play the game and use all the DLCs before without any issue.

Has anyone had a similar problem or knows a fix?

Thanks in advance!