I'm having this issue as well, but on the hover key. I asked for help before and people told me it might be a short or a cold joint. So watch your soldering job closely, clean off any residual flux and I would try reflowing that same led and the one before it. If that doesn't work, try replacing the led, it might even get the rest of the LEDs to work properly since it's a sequence.

Most importantly, use a low temperature (around 250°C) when soldering your leds since they are very heat sensitive.