i have a master tier subscription, which i read was required for using other peoples' homebrew in your own character creation. but as i got to the species tab, no homebrew options showed up at all. i have a few different homebrew species added to my collection, so i'm not sure what the issue is, and all the other forum posts i found were from several years ago, and seem to have been caused by something else entirely. any advice/tips would be welcome, thanks!

Yes I did. I even did the classic "turn it off and back on again" maneuver, which did not work. 

What DID end up working, somehow, was purchasing some content. I purchased the Mordenkainen Monsters of the Multiverse sourcebook because I was frustrated by the homebrew not functioning, and as soon as I went to apply the similar species that was in the Mordenkainen book, the homebrew species were visible. 

Obviously this isn't anyone's fault but it seems like some sort of bug that it took me purchasing content for homebrew material to become available.