Instrument lights stopped working

A few bulbs used for instrument lighting were blown, one for the right LCD display and the one behind the left part of the speedometer. I have changed a couple of the bulbs before, but this time I decided to change them all. I reused the sockets, just changed the bulbs.

I unhooked the negative on the battery before unhooking the instrument panel cable to change the bulbs. I plugged it back in after bulb replacement, reattached the battery, turned the key two clicks, turned the main light switch and found that everything was working fine except for the bulb lighting the right of the speedometer.

I turned off the ignition and twisted the socket to release the bulb. (I forgot to unhook the battery this time.) I checked that the socket contacts were all OK and twisted it back into place. When I turn the ignition key two clicks to turn on the lights, both LCD panels are lit up. This shouldn't happen with the main light switch in the zero position. I then turn it once and twice to the right to turn the instrument lights on too. It doesn't happen, the instrument lights stay dark and the LCD panel lights are turned off too.

Any ideas why this happened and how to fix it?