The user gets automatically log out because of one of the following reasons:
Session expired: The session of the user is expired. The organisation admin can set ‘Session expiration time-period’ and based on the setting, all the users are automatically logged out. Please get in touch with your administrator to know the exact time set for session expiration
Removed from the organisation or channel: You might also be logged out when the admin removes you from the organisation or from the channel where you were last active.
In case you are getting logged out for some other reason, please contact us at firstname.lastname@example.org