Hi @ualjp,
I was working on the plugin for a while, in the current version of the plugin (1.1.1) the user registration with ORCID is not working with OJS 3.1.2. The issue is known and I just filed it today: https://github.com/pkp/pkp-lib/issues/4601
We are still working on a solution.
But you should be able to use Sandbox credentials and should be able to connect the ORCID iD from the User profile page . See the public tab and connect and authenticate ORCID iD with the button.
Regards,
Nils Weiher