You need to create a specific application password to use the remote posting features of SCM.
This password is needed so that json api poster will work.
The app password IS NOT the same as your admin login password.
1] Login to WP and find the user details of your Administrator account.
2] Click on username to open profile page. Scroll down to Application Password section.
3] Create a new password, click Add New…
4] Copy password and use it in SCM.
5] Inside WP Poster.
6] Add your blog
7] Fill out details, paste in App Password
8] Force SCM to use JSON API first by going to Settings > Use Wordpress XML RPC = 0
This is done automatically on newer SCM installs.