Boot fanfare, but black screen after reassembly

Hello folks!

I’ve attempted the upper case assembly replacement guide here on iFixit, to replace the keyboard on my 2016 Retina MacBook.

I followed the instructions and was careful to completely drain the battery first, make sure the battery LED was turned off inside, etc, and that all screws went back into the same place.

After reassembly, the screen will not turn on. Here’s more info about my issue:

At first, the USB-C cable “chime” sound and power button boot-sound were very sporadic, sometimes I got the boot sound, sometimes not. After doing a PRAM and SMC-reset, this seemed to stabilize. Now I get the charging sound every time I plug in my cable, and the power button gives me the boot sound every time (and makes the trackpad clickable). Holding the power button turns the computer off, indicated by the trackpad becoming non-clickable.

All the while, the screen is black. I’ve tried re-seating the display cable (with the connector tab closed, as per instructions) to no avail.

1. The keyboard is compatible with my model (A1534), but I noticed the keys were clickier on my old keyboard, so I don’t think it’s the exact same revision. Could this be the cause?
2. The replacement keyboard is a UK variant, while my laptop is Swedish. The physical buttons are all in the same place, except that instead of Å, Ä Ö, there are [ ] symbols instead, etc. Could this be what’s messing up the screen?
3. Have I accidentally zapped something?

I realize I have an issue, even if it’s not something I can fix on my own – can anyone give me hints on good ways to troubleshoot and find what the issue is, exactly?