April 2018
So, my sister and I are playing The Sims Mobile and she just updated her game around 2 days ago, when she told me, "How do you increase the coins? you only get 10 per event." So i told her to go to her QUESTS page to find the ASOS event to get 40 coins and lo and behold, it's NOT THERE! so we went to the market place and the event is there, but no pink A to start the event and to uncover the clothes. She really wants to unlock the photography hobby and career too. (She started later than me, and my game's working fine).
PS: I asked on her behalf since she doesnt have an account here.
April 2018
That's a known bug sadly:
https://answers.ea.com/t5/Bug-Reports/Open-Can-t-start-ASOS-event-on-Market-Square/td-p/6762209