killoooovet , please read the earlier post where i advised not to do anything to the other still working players. i assume that the v3.5.37 currently works, so leave it as it is and don't do anything to the firmware. There is no such thing as firmware updates, and you will most likely 99% brick your player if you performed an update.
You will need to install MP3 Utilities, available in the Downloads > Tools section of the forum, any version would work. Once installed, there would be MP3 Utilities Upgrade Tool used to flash firmwares. The guide is here
http://www.mympxplayer.org/how-to-up...ayer-vt46.html
For the bricked player with the original v9.0.50, try all the firmwares in here
http://www.mympxplayer.org/actions-9...mare-dc37.html