3.6.15 "Your session was invalidated by a different browser"

the 3.6.15 version dose not work for our system. we need multiple logins because we have various users and there is a constant error to the other users.
the error is “your session was invalidated by a different browser”. the users can never use this version we are stuck on 3.6.15
i tried deleting the admin login table. and it still dose not work!

we need it to work for other users

we are stuck on 3.6.14