asdf maintainer here. There couple that could be causing this. If what @massimo said did not work, I’d suggest re-reading the asdf getting started guide (Getting Started | asdf) and make sure you follow the instructions for your operating system and interactive shell.

If you do all that and it still doesn’t work, it means there something else interfering with asdf in your shell. I’ve found the following commands to be helpful when debugging versions installed with asdf:

type -a mix
type -a elixir

Both of these commands should print out a one or more paths to mix and elixir executables on your machine. If things are working properly you should see the asdf shim paths listed first ($HOME/.asdf/shims/mix and $HOME/.asdf/shims/elixir).

two things you can try

asdf reshim

and

export PATH=~/.asdf/shims:$PATH

Literally couldn’t figure out this issue over the last 3 hours and you post this 2 hours ago lol, thank you!

For anyone too lazy to open the link, remove all lines related to asdf from your .zshrc and add the following line:
export PATH="${ASDF_DATA_DIR:-$HOME/.asdf}/shims:$PATH"

Then, for good measure, run asdf reshim and close all terminal windows before trying to run mix ... again.

Is mix binary present in $HOME/.asdf/shims/mix? Did you do asdf global elixir (version)?

Same effect should be achievable by running asdf global elixir 1.13.2-otp-24 btw.