> Is it a problem if I haven't seen CL:E?

It will not be a problem if you have not seen the show! Though, if you haven't seen CL:E, that is even less of an issue. Since the RP starts before that time period, the events of CL:E will become altered by this alternate universe, thus making it different. Events having happened in CL:E will be mentioned, and even changed, and will include spoilers within the RP. But, if you haven't seen it, that doesn't matter. I wouldn't mind people who don't know anything about CL in the first place to join! That way, they get a fresh start and are more shocked and realistic when their characters encounter things.