From what I’ve been reading, Plex is transitioning the download feature to require a Plex Pass for the user who wants to download (for mobile sync this used to be linked to the server owner having a Plex Pass).
Have you already tried to restart the server and clients after changing those settings? Shouldn’t be required but sometimes it can help if something gets stuck.
Currently, during this opt-in period, Downloads can only be used with a server who’s admin has a Plex Pass. This will be opened up to all servers once the opt-in period is over. This is mentioned in our FAQ.