The deck appears here
Can you go to browse → tags → #AK_Step1_V12 → then enable this option
This will tell you where your deck is hiding
For example, mine says AnKing Step Deck (see below), yours might say another deck which is where the deck actually is
After this, you can move all the cards by following this tutorial: It says my AnKing deck was installed, but I can't see the new deck