Not Found when getting an authorization code

I read the document on OAuth2 authorization and went to http://my.mautic.base/oauth/v2/authorize?client_id=my_client_id&grant_type=authorization_code&redirect_uri=http%3A%2F%2F127.0.0.1%2Fcallback%2Ffor%2Foauth2&response_type=code&state=yddtxdmq via Chrome to get an authorization code. I was prompted to login there, and I got Not Found error after logging in. In my API credentials, the callback URI is http://127.0.0.1/callback/for/oauth2.

Why I cannot get an authorization code?