Are you saying you claimed that 10+1 voucher and it's not appearing on the relics page? Or did you claim it and then attempt to open it?
If you attempted to open it and then the game crashed, you should still have 11 new fighters in your collection. You can see them by using the 'recent' sort option in your Collection.
If you never received the relics at all, you'll need to contact customer service at skullgirlsmobile.com/contact so they can investigate your account.