The only time you can click the button to open a draft or create a new topic on the forums is if you are on the main forum directory or a subcategory page, like Quests. Trying to click it on any large category page, like Gameplay, does not work. I recently reported another issue with the CSS being messed up on the same main category pages on mobile, so it seems like that page is having issues, in general. This button issue has been problematic for awhile, though. Viewing on Chrome.