This is an extra step in the most recent ORCID plugin that checks whether you have set up the plugin.
You won’t be able to enable the plugin until ORCID API credentials have been entered in its Settings. Without these credentials, the plugin would be sending sandbox URLs to authors that’s why the decision was made to prevent enabling it unless it’s set up.
I know that pop up that says “plugin enabled” is misleading - it’s yet to be modified because it’s a fairly recent change to the ORCID plugin.
For the ORCID Plugin setup instructions follow - How to Set Up the ORCID Plugin in OJS and OPS