1987 420 SEL had since new now trunk will not unlock; Key turns left to alarm auto then turns right to unlock push in button but trunk dosen't open?????

 

I've never owned an '87 420 SEL, but I've had a couple of cars in my lifetime with trunks that would stick like you're describing. It's always been caused (on mine) from the locking mechanism becoming mis-aligned from normal use over time.

Is that a manual locking mechanism on your car? If yes, try pushing down on the trunk lid then push the button. Also try jiggling the lid up and down with and without the button pushed. If you get it open, adjust and lubricate the locking mechanism.

 

seen to be the trunk vaccum actuator broken or leaking the vaccum .make sure your key lock not on this -- position .is at | upward position.....