groupMember is not working

Hi Team,
Any idea why groupMember is not working. When try with REST API as well. It is not working.
I am not getting why . Can someone help me on this ?

List groups = identityService.createGroupQuery().groupMember(userId).list(); // Not working
List managerGroups = identityService.createGroupQuery()
.groupType(“Group”)
.list(); // Working

http://localhost:8080/engine-rest/user?memberOfGroup=‘group’ // Not working

How are you getting userId?

Using Identity service based on login user.