Depending on your settings, Wise Owl Legal may log out out of Wise Owl due to a number of reasons.
If you have been inactive for a period of time, you will be logged out.
This time can be changed by going to Tools & Settings > Manage User > Choose user > Account > Login Timeout
You may also be logged out or 'kicked' off Wise Owl Legal if there is an update going on.
You will be informed of any times that you would be unable to use WOL during these updates.