How do i reset box pls

Hi all,

I did try and find my answer in forums but to no real avail...

My lad took the box from one bedroom to his which we've done plenty if times but when he turned on it just came up with minix and green Android man below.

I tried turning on without hdmi connected as suggested in other thread.

So I unplugged stuck pin in reset hole and powered up and the screen was initially blank but after about 5 mins or so started to get this....

E: failed to mount/ cache (invalid argument)

Then...

How do i reset box pls