Is it only that it's not visible on the forum index or are you unable to access it directly via an external link, as well?
Reos Mods If clicking that takes you there just fine you can bookmark or subscribe to the forum for quick access
As for what else you might be "missing out on" there are some other things Tapatalk cannot do. The classifieds section or any other area that requires a web form to be filled out is not accessible via Tapatalk, though the bulk of the discussion forums you should still be able to access just fine