HP 8600 officejet pro engineering Menu - reset menu (printhead error) Which method for menu?

[yellowtree]

I have an HP 8600 officejet pro. 

I have used the technique to go the the engineering menu as

             press HOME - Press BACK - Press HOME - Press HOME 

This technique has always worked for me and there is a YouTube video showing this technique used.

Now I see the technique 

            press BACK - press BACK - press BACK - Press BACK

I have never used this technique.

Which is correct?

I have a missing printhead error message so neither button (home or back) appears but I am sure I am hit the right spots.

What have I tried:

      -- I tried waiting until the error message appears and trying both methods  -  nothing

      -- I tried pressing the buttons during boot (only had the status bar on menu) - nothing

    - What am I doing wrong and which is the correct method?

           (has the updated firmware changed the method?)

    - I am going to install a new printhead but now want to know how to get pass this error to reset the printer, if necessary.

Besides using software to reset the printer is there a hardware way to do a hard reset.  The problem is the printer has only a screen, on/off button, and a plug.  I can access the printer by the Ethernet but I cannot find an option to reset.

Thank you for your time and help

[Valsimot · Accepted solution]

You are not doing anything wrong and you have the correct steps. Once you get a printhead error like yours, all menus are not reachable.