Thanks for the clarification, one more request, tried tracing from landing page but it is not getting traced. And after login I have disconnected the network and I am able create temporary but it is not getting sync after connecting to the network again.
Some where I have seen case can be created in offline as well.
Identifying correct requestor on System landing page is a bit cumbersome. You need to look for same operator of type APP.
As long as your case and access group are offline-enabled, cases should work in offline and get synced when connected to network. Can you post a screenshot. Try logging in again while network is connected.
Failing sync request is the main problem here. Can you remote trace and post if there are any failures? To trace - go to System -> Operations -> Requestor management -> Filter with your Operator ID -> Remote trace the one with type APP.