IIS Applicaiton auto logout

In Windows Server 2012, I have IIS 8 installed. For one IIS application, I am using an application pool. I try to increase the Maximum Worker Processes to 10, however, when I open the website in a browser, it will auto log out when I click any link. When I change back the Maximum Worker Processes to 1. The log out will not happen. But in another server, the same website with Maximum Worker Processes 16, the auto log out will not happen. Why the maximum worker processes will cause the website to auto log out? How can I solve it?