ASP.Net: Multiple machines Session logging out at same time in different locations at same time

We have uploaded our webapplication to an ibm cloud server. All our clients are accessing the application via a domain name. we are using c# and sql server 2014.

Our issue is all our client machines are getting logged out at same time. We are checking the session for login and logout. when a user's session is timed out that machine will be logged out... Now the issue is all the client machines(at different locations) are getting logged at same time.

Please help me with this issue.