I recently solved the problem and managed to update my Roku to the latest firmware. I remembered that there is a reset button on my Roku - I pressed it down firmly and rebooted Roku several times going through the same update loop, and after a dosen iteration it finally updated correctly, and my Roku 3400X is usable again.
i kept restarting and resetting the stick for at least an hour, went through endless looping and still nothing . I'll try again today to see if i get lucky. Also, is there a Roku dev helping on this? already tried support through email and phone without any luck, got hung up on the phone and its been 2 weeks since my email to support team, and still havent got any reply.
Do not expect a reply, I did not get it. Maybe that was because I did not use any paid services.
One more thing about resetting: I read somewhere that you need to hold the Reset button pressed down for at least thirty seconds, so what I did was press it down first, then plug Roku to the MHL port and hold it the whole time. There is no reaction from Roku to this, the lights blink sometimes but on the screen it is just an ordinary boot up and working, so there is no way to see if the reset went throught. It just happened that after some time it update correctly. You will be able to see it immediately if instead of three steps in checking the network it will start going only through 2 steps.