I was bored and found a HP-27S

[franz.b]

I found out a few things. first of all it is alive.
I managed to lock the pcb on the keyboard by inserting small pieces of metal into the hooks so as not to twist them, but it still did not turn on. then I short-circuited the terminals leading to the keyboard in correspondence with the ON key and it finally turned on, but the ON key is the only one that doesn't respond!
With a lens I saw that the conductive trace P2 is interrupted, yet at a preliminary check it worked, I must have broken it!
Now I have to repair it, the part that protrudes from the sheet is still functional, I have the idea of using a conductive pen, you say it can work? I've never used it and I don't know if the ink adheres and detaches from the plastic ... do you have any other solution ideas?
Also I found that the external screen protector is not polarized, the polarization is part of the lcd.

thanks in advance for any suggestions.