If you get an error “User Session Closed After Timeout” for your WebDynPro (HTTP/SMTP/Etc..) sessions then you should check the following solutions.
You got a message in your SM21 log like –> TH_SET_AUTO_LOGOUT
Solution 1
Change the parameter rdisp/plugin_auto_logout like below
Go to transaction code –> RZ10
Add / Change the parameter ;
Save the profile
Activate the profile
Solution 2
Increase the http/security_session_timeout to a higher value (default value is 1800).