Always give this message "Sorry, but you are either not logged in, or something is preventing your browser from handling cookies."
You probably need to enable cookies in your Firefox:
I did all these and i enabled the cookies but it still the same
You may be having a problem with some extension that is hindering your Firefox's normal behavior. Have you tried disabling all extensions (just to check), to see if Firefox goes back to normal?
How to do that ?
See this for how to troubleshoot problems with extensions: