Main thing is - create only ONE account for ProBoards (global account) THEN create another username/account here. You have to register two separate times. (Or however many times for as many different forums)
(Chances are you are trying to login here with a username that is from a different forum, log out of everything and log back into your global then try it again. Also make sure that you aren't changing the password for the global account each time, thinking you are registering here. 😉)
also another thing to try is to click that middle icon at the bottom right in between the people talking and the gear, that brings up the “forum dashboard”. It shows all of the forums you are signed up for under your global account.
the name here is “Weight Watchers Message Board” and if you are signed up for it, whatever name you are signed up for will be there underneath. From there you can edit your passwords if you click the blue “account” tab.