Answer:“Music doesn’t play when device is off” – Music Video.s Play.er for Youtube Music Stream.ing Review

Just in general YouTube doesn’t let people play music when the device is turned off. Considering this app is based off of YouTube it does the same thing; not let music play when device is off. This is something that people should understand and not be surprised about, since as said the app is based off of YouTube and will have features the same as YouTube.
Review by Helping500 on Music Video.s Play.er for Youtube Music Stream.ing.