Hi,
The plugin works perfectly on multisite configurations, users must belong to the list of users of the sub-site to be able to use the REST there, however, if you require all your registered users in a sub-site to be able to use of the resources of another sub-site, then it will be necessary to make a couple of changes in your file class-jwt-auth-public.php
where it says get_bloginfo ('url')
should be replaced by network_site_url()
lines 142 and 278.
Hope this helps you,