Hi!
This is most likely an software issue.. So if I'm correct, it failed after you've tried to install a firmware update for this device?
If this is the case, the best thing to do is to contact Miyoo. You could replace the motherboard to fix it, but this will be expensive.
Hopefully Miyoo do have something to re-flash the device so that it can be used again instead of replacing the motherboard....
If you are wondering regarding the motherboard replacement, here is a video: https://www.youtube.com/watch?v=6R2h4kfW9Mg
Please let us know how it goes!