Update : Got the sound back!!! – Sight Words Reading Games ABC Review

I just fixed the problem! I clicked the “app support” and follow the instruction step by step. So I went to settings, sounds, lock sound. Then I swipped the lock sound button from “white” to “green”, and the sound works again! That’s it! FYI my iPad mini use iOS 11.2.6. Thanks for the clear instruction.
Review by Lanny Anderson on Sight Words Reading Games ABC.