The 2020 Valentines challange isn’t showing to play
Have you done any of the quests?
pixel_player27303240 The challenges usually unlock after the 1st mine is complete.
Check your Quest Tab. There's a quest requiring you to VISIT the Challenges for them to open.
In addition to what gamemaster, Abhi & BlameTheParrot said above.
Check out the maps, videos, walkthroughs, guides & hidden gifts/bonuses in these links