When does the Ceramic Speed Mission and the Tour For All challenges appear in the top left of the screen for accepting the challenges?
Where you select routes (at least on the computer). Apparently you can sign up online though too
I did that, they appeared on my Android phone but not on my tv screen when I turned Zwift on.
Are you referring to the mission like below (Ceramicspeed Mission). The mission should appear if you are on the latest version of the Zwift software.
Always make sure you are running the latest update. On PC it should check when you start up. Not sure about other platforms but if you don;t have the update the mission does not appear.