I have noticed these past few hours that the command "/is coop (player)" does not seem to be working with members of an island. Hopefully this command is able to be fixed. Also, this command does not show up on the island help list "/is help" ~Ted
If /is coop doesn't work for you, please be more specific in describing what about the command is not working so that it is easier for us to identify the issue.
Good catch, we implemented a new ranking structure last night that resolves a huge legacy issue we've been facing for over 2 years, so some new permissions may have accidentally been missed, such as this one. It has been added back now. Thanks