Stuck in Do Not Disturb

I have two RCA tablets. They worked great for about 6 month. Now they are both getting stuck in "do not disturb" mode. I will select end now, or try the timer or have even done factory resets multiple times. It doesn't matter what app they are in the sound will completely disappear. I do not know how to disable DO NOT DISTURB so that my children can enjoy their tablets and watching netflix and their learning games. It is making me a very unhappy mommy. I have since bought my younger daughter a new tablet as I could not get that one working at all and now her new tablet isn't compatible with netflix downloads and is starting to glitche to DO NOT DISTURB as well. Please help