Our Craft installation is now working on the Production Cloud-Server, except that if I'm logged in the CP, after maybe 30 sec the login-modal pops up and says that the session has expired. If I just reload the CP, I'm in again without the need to login.
That behaviour didn't show up on the development server. I didn't make any Configuration Settings like userSessionDuration or something like that, that's all default.
Any idea?