We managed to setup LDAP as a secondary User Store in the WSO2 Governance Registry Management Console 5.3.0 (Carbon). We see the Users/Roles were loaded correctly and we can access Management Console (Carbon) with those users.
However despite of the LDAP users having "Internal/store" permission, they cannot access/sign in to WSO2 Governance Center - STORE. The error on the Sign In page is: "Insufficient priveleages to access the Store application."
Managed to solve the problem just with putting the domain name of the User Store and forward slash in front of the LDAP username: <domain_name>/<user_name>
When the username is specified without the domain name, the Store application gives misleading error: "Insufficient priveleages to access the Store application." I think it should respond with different error, for example: "The provided username and password combination is incorrect."