I would suggst you have a read of the Help FAQ which I am sure will give you the answer to the problem you are having.

Forest of Dean Parish Records Help FAQ
http://www.forest-of-dean.net/members_faq.html

As you have successfully logged into the Message Board to post your message, I suspect the following which I have just copied from the FAQ is the reason.

"The registration for the Members Area is separate issue to the registration of the Message Board.
You will need to do a separate registration for each."