I think that rules out some kind of error with your account, unless it's somehow Firefox specific.
Are you browsing for more than 10-15 mins in one session (a session being the time between logging in and when you close Firefox)? For instance, does it log you out after one hour of browsing? If not, it means your browser has correctly received and is using our cookie. If that is the case, I'm a bit puzzled by this one. Is it possible you've set some site specific cookie policy for the Org in Firefox?
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