4WD engages no dash light thoughts?

1990 4x4 MT W/ADD

4WD does engage in 4H and 4L have confirmed this multiple times. Replaced sensor on front differential and sensor on transfer case just in case. I replaced the bulbs in the dash cluster with LEDs. Now I will say I specifically put an incandescent bulb in the 4WD light slot because I didn't know if I would have the time to test the polarity of the LED. It's my daily and I was running out of time that night.

Question for the enterprise is what am I missing that is not causing the dash light to come on when in 4WD. Everything else functions as it should I'm perplexed. I'll be redoing the vacuum lines for the VSVs this weekend since I'll finally have time for once. But as I understand it if the VSVs were leaking or having malfunctions my 4WD would not engage. I am also under the impression the sensor on the T-case and front diff are what would sense and trigger the light to come on in the dash?

I am by no means a mechanic but I am mechanically inclined. Just wanted to see if anyone else may have an idea of what I am missing.