It's possible that its a broken link in the mobile version of the page but works fine in the full page.
Try requesting the desktop version of the page and see if the link works.
EDIT: Confirmed, in the mobile version of the page, you select the menu and then select "Forums" and it takes you to a login for the main PCS website because the link is I think mispelt as @polycrac suggests. (using Firefox on IOS 12.4)