Box not working after power cut.

[adm]

I've tried the switch on the back on and off several times, but it doesn't help.
I have disconnected the power (power cable) from the receiver I will switch on in 30 minutes. Maybe this will help.

Around 5 minutes should be enough. You just have to leave the box long enough for all the internal power supplies to discharge, something that doesn't happen when the box is in standby or deep standby.

If not, does that mean the receiver is gone?

If the box lost power while hard disk or usb stick was being written to it could have corrupted the data.

If after the power off doesn't work:
Try a USB flash of the image.
Try disconnecting hard disks.

file:///C:/Users/alan/Downloads/How%20to%20flash%20a%20VU+%20Uno4K%20SE.pdf

On these boxes the image is stored in flash memory and to boot don't need a hard disk or usb sticks etc. Flash memories have a secure area which can be protected and possibly this is where the code to allow a re-flash lives, hence you may/will be able to recover some corruption with a USB flash.