Locks: who is in which profile
A profile can be open for only one person on one computer at a time. This keeps the data from diverging.
What others see
An In use button, and under the name — “Open: email, computer”. The Now tab shows who is in which profiles.
Release the lock
Right-click → Release lock. Do this only if you're sure the profile is really closed there (for example, the computer shut down). The action is recorded in the activity log.
After closing
While the profile's data is being sent to the server, it's shown as “Saving data”. This takes a few seconds, then the profile is released.