No backlight after battery replacement

Hi,

I just replace the battery of my Dell Inspiron 7306 2n1. I only disconnected the battery cable to replace with the new one, no problem with battery connectors and computer power on. But I first noticed I got problems with my keyboard.

First is that several letters (e.g. o, l, p) did not write anything on screen unless applying high pressure on the touch.

Second is that I don't have backlight anymore (nor the shift lock key light when CAP LOCK).

I reopened my computer unscrew and screw again battery and slightly move the cables, without touching the connectors. I once get the light on Shift lock key back, but still no backlight. Finally, after several try, I now get all my keys back, but I lost all light on my keyboard.

I am scared to reopen my computer and lose again my keys...

How can I know where I have to look in my hardware to check backlight, is there any schematics? Do you know how the backlight could have been impacted with my battery replacement? Why are my keyboard keys so sensible when opening my computer?

Thanks for your insights!