MicroTik Router RB750 downgrade ,after reboot , not access

MicroTik Router RB750 downgrade but after reboot , not access !!

I can not access the Router now … please help

From what version to what version did you downgrade? You can reinstall RouterOS with Netinstall: http://wiki.mikrotik.com/wiki/Netinstall

It was from 5.9 to 4.17 , I was trying to use Netinstall , it does not work.

I was trying to reset - to hold the reset button it does not work…

fade up!!