webadmin console not accessible

After upgrading to LSWS 5.4.1,while logging into webadmin console it is showing many warning and not able to login.I even downgraded to 5.4 and still the error is not resolved. The warnings displayed are below. Warning: session_start()...

... and the support plays ping-pong with you for days without presenting a solution: I found a super simple solution that helped in my case (on page 23 of Google`s search results.) cfs -f The support was not able to tell me that simple and in retrospective obvious command. Hopefully, it will...