Issue with OAuth2 "error:invalid_client"

Following this and this links to understand about monitors and create some funny and good playlists on Spotify, I’m facing about this error below:

error: invalid_client

The error appear just on POST Get Auth Key

Below some screenshots:


Pre-request Script:


PS: On Auth, I tried to follow a similar question that I found here, and I changed the “Client Authentication” to “Send client credentials in body”, but not worked:

Any help to solve this error?

Thank You!
Denis Cardoso