Unfortunately, recently more and more sites fail to work with Tor Browser. Notably, I am informed by people who are not me, Anna's archive and libgen.
In theory you could use Tor browser with Tor stripped (I heard this is what mullvad browser is?) or go tor-then-proxy (this is what I often do, because I sometimes use whonix at work). I don't know about libgen or Anna's archive, I don't use them.