When you say that you turned it on and there was no signal, did you mean that the Mi Box front light was on but there was no picture? Or that the light wasn't on and the Mi Box wouldn't power on at all?

That would be two different problems and you may have made it worse, sorry to say.

As for the MDZ-16-AB flashing using Amlogic USB Burning Tool, it appears not to be a solution. ( https://forum.xda-developers.com/android-stick--console-computers/amlogic/s905x-help-mi-box-android-tv-mdz-16-ab-t3477286/page9 ).

There are a few suggestions scattered throughout that thread you may want to try. Including trying to reboot via your computer. Although referring to trying to root, it says to reboot in your connected computer, in a shell, type "adb root" type "adb shell setenforce 0".

Keep in mind that most of that thread is about rooting your Mi Box which is not a good idea for most users right now. Hell, you may want to try it since you can only get so far with your box now. Worse thing happens and it bricks (similar to what you have now), best result would be that you can get it working and go from there to get it stock.

Your best bet, I think, is to contact Xiaomi support. They may say your SOL, but maybe they can give you the firmware you need or help you through menus to try and fix everything. You may not want to say what you said here because they can come back with "sorry, you voided your warranty". They wouldn't be the first company to say that. There is reference to another website, but it is in Russian and translation tools doesn't translate enough to see if it is useful. Incase you want to see if you can decipher it or if you know Russian, that site is: http://4pda.ru/forum/index.php?showtopic=399304&st=1080#entry34714599

If your box shows any sign of life, you can force it to recovery mode.

You must have a FAT32 formatted USB thumb drive containing a ZIP file renamed to update-once.zip and a text file named xiaomi_update

You will need the proper update file in zip format. DO NOT UNZIP!!! rename the zip file to update-once.zip

There must be one other text file, named xiaomi_update in the usb drive which includes the following text....

--update_package=/udisk/update-once.zip --wipe_data

Insert the formatted USB thumb drive into the USB port on the Xiaomi box

There is a tricky method for forcing this device into recovery mode. You may benefit from an extra pair of small hands to perform these gymnastics.

1-remove ac connector from the unit

2-press the small left key on the remote (BACK)

3-press the large, round OK key on the remote. (Make sure you are pressing firmly in the middle and do not touch any surrounding directional keys.

4-point the remote at the front of the Xiaomi box

5-keep the remote keys pressed and

6-replace the ac connector fully in its socket on the Xiaomi box

7-Keep the proper remote keys depressed for at least 10 seconds

Your box should power on with the recovery screen menu

Follow instructions for recovery and use the remote keys to navigate to EXT and choose the update.zip file from your usb drive.

Rinse, repeat if you do not succeed. You will ultimately gain access to the recovery menu by following these steps carefully.

Good luck