I'm getting "no :user configuration option found"

[DiegoUreno]

I've been following How to use Pow in an API instructions and i'm getting the next error:
"Request: POST /api/registration
** (exit) an exception was raised:
** (Pow.Config.ConfigError) No :user configuration option found.
(pow 1.0.26) lib/pow/config.ex:56: Pow.Config.raise_error/1
(pow 1.0.26) lib/pow/ecto/context.ex:131: Pow.Ecto.Context.cr"

This happen when I do a post request to localhost:4000/api/v1/registration I've seen other issues where the solution was:
"Make sure that :my_app in plug Pow.Plug.Session, otp_app: :my_app correspond with the one in config config :my_app, :pow,.

Originally posted by @danschultzer in #319 (comment)"

But in my case it's seems to be alright, i've checked and double checked that but i'm still not getting it, idk what to do now.