What does that mean exactly, what in openHAB represents “your clients”, where are you viewing this state?
To clarify the item.state is returning online per the PaperUI Control page.
Unifi binding gives you a lastSeen channel to be linked to a DateTime type Item.
This was my understanding and now I believe it is correct, it looks like the logs are recording the LastSeen in the same format as other bindings such as Astro but it displays differently on the PaperUI Control page. So I guess I no longer think that the datetime format is the issue.
2020-03-28 21:01:21.091 [vent.ItemStateChangedEvent] - Chelsey_LastSeen changed from 2020-03-28T21:01:00.000+0000 to 2020-03-28T21:01:14.000+0000
2020-03-28 21:01:21.093 [vent.ItemStateChangedEvent] - Kyle_LastSeen changed from 2020-03-28T21:01:00.000+0000 to 2020-03-28T21:01:14.000+0000