https://wiki.mobileread.com/wiki/Kindle_Serial_Numbers
G090G1 | Kindle PaperWhite 3 (2015) WiFi | PW3 | [Support added in KindleTool 1.6.5]
It should be supported...
However, you did not mention the results of step #4, nor did you mention if the checksum test was done. Are you sure your download is complete and uncorrupted?
Also, you report that step #6 fails, but you did not mention doing step #5. I suggest starting over and do it correctly this time, with no variation from doing every step without exception.
Please report everything in your next attempt, so that we can better help you.