I replaced the odometer gears on my 94 K75 and all went well. Also replaced the backlight bulbs with led's. Everything appears neat and tidy, and I was careful with the ribbon installation, but the backlight bulbs won't light; although the brake, abs, high beam bulbs all work at the turn of the key.
The backlights are supposed to work at the turn of the key, correct? Is there perhaps an easy explanation, or test I can do? Is there a particular connection that may be the culprit? 
If it were only one or two of the four led's I could understand a bad connection, but not all 4.

Some LEDs are polarized. Try rotating them 180 degrees.

You can test many (not all)  12V LED bulbs with a 9V battery if you have one handy.

Are you turning the key when it's parked in the dark?

Polarity was part of the equation. Also, I thought that the rim of copper was all that was needed, then realized that a tab of the copper needs to down into the socket opening. All is well. Thanks for the help.

You saw the light! Hallelujah!

Now I'm so happy, no sorrows in sight! 
Thanks to forum members
I saw the light