I can't see any reason that you can't post. The "help" section is not very useful and seems very general, and not written specifically for this forum. I seem to remember that one needed to have made 100 posts to be able to start a topic in the Seconds Out forum - but you have, of course. The only thing I can think of is to make sure you are logged in.
Hopefully, someone else "in the know" will chip in.