This is what I get, its funtoo linux though…
$ mix help | egrep "phx|phoenix"
mix local.phoenix # Updates Phoenix locally
mix local.phx # Updates the Phoenix project generator locally
mix phoenix.new # Creates a new Phoenix v1.3.0 application
mix phx.new # Creates a new Phoenix v1.3.0 application
mix phx.new.ecto # Creates a new Ecto project within an umbrella project
mix phx.new.web # Creates a new Phoenix web project within an umbrella project
Of course you need to make sure that you are actually using the correct elixir version!
In your case I’d try this to be sure:
$ ASDF_ELIXIR_VERSION=1.5.1 mix help | egrep "phoenix|phx"
If that does really print nothing, please do show the full output of
ASDF_ELIXIR_VERSION=1.5.1 mix help and