4wd issue

First post, hoping someone can help shed some light.

My Hiace: 1991 manual, 4wd manual locking hubs, 3L
Issue: I was driving along and noticed the 4wd push button was depressed unbeknownst to me. I thought it odd as I was sure I didn't press it (I blame it on my girlfriend 😆) . Who knows how long I had been driving with that button pressed in. When it finally came time where I needed 4wd, locked the hubs, pushed the button, and nothing. No green light AND the hi / lo shifter isn't moving (stuck in forward position; hi 4). Afraid for the worst but want to hear thoughts before I stress to much. Thus far I have checked the fuses, played with the vacuum hoses, and tried to engage and then drive forward and or reverse a bit. Thank you!

Well, it could be the button is broken? Have you tried to measure if there is any contact through the switch if it is pressed?

If you have your girlfriend sit in the car and push the button a couple of times (with key to ON, but engine not running yet), and you go under the car, you should hear the actuator clicking. You can see where it is, it is a flat square box with some vacuum tubing on top. If you don't hear it clicking, try it with running the engine.
By clicking I really mean the actuators which should sound like a relay clicking. The "cloink" sound you get when it goes into 4x4 should be noticeable while inside.
(You could also disconnect the vacuum tubes to the gearbox, so you should at least here an air sucking sound when the button is pressed)

You could also measure the plug on the actuator. But I don't know if it is switched on getting 12V or not, or if it is switched to ground.

Ok I measured the button which is in working order and also had GF sit in the van and press button. I AM hearing the click so maybe can rule out the actuators.

Ok so next step is your vacuum. So is braking functioning normally? No other dashboard lights indicating an issue?

Perhaps you can disconnect the tubes between actuator and gearbox to feel if it is sucking air.

the vacuum tube going to the actuator starts at the alternator/vacuum pump, runs down the body to the back. Perhaps it is clogged or it is bend/under high angle so no air can get through.

Did you ever use 4x4? Has it ever worked?

Mine (a 94ish) has no dash light when 4wd is engaged. Also, my hi/lo lever is very stiff.

I had to get mine stuck in 2wd to prove to myself that 4wd was working ok

As as aside, I'm not sure what damage could occur running with 4wd engaged, but with the hubs freewheeling? The front driveshafts will be rotating, but with no load on them?

Thanks for the responses so far.

Concerning the vacuum. Braking is functioning normal with no dash light indicators. I have pulled the vacuum lines off and there seems to be suction although not super powerful. The 4x4 has worked before, prior to the accidental button press. I accidentally broke the small plastic male part where the tube fits onto. DOH. But don't think the vacuum is the issue.

Well, there is a small vacuum tank near the actuators. When the engine has run for a small time, it should have quite some build up of vacuum power. It should be noticeable when you pull the line.

What you could do is swap the vacuum lines, so I think it should enable 4wd even though button is not pressed. The only way you can verify that the 4wd is working then is to put it into low gearing.
Always drive a couple of meters to make sure it has a chance to enable it.
Another test is to hook it up directly (bypassing the actuator)

I think you (or with a mechanic) need to verify that the vacuum part is working correctly.
Because the next step is removing transfer case and check internals. Although you could try to replace the oil first.