Why wont the trunl latch close on a 2001 mercedes s class?

sounds like you have the child locks on :)
Look for a small lever on the side of each door under/by the door latch. it probably shows a padlock open/closed. try moving it !

May be a blown fuse or bad connection, Check for voltage at the boot latch.

Have you cleaned and lubed the spring?

undo the trunk release latch to see if trunk stays shut. if it does then check for stuck release button or short to ground on that circuit.

I don't think there is a day that goes by in the shop where we don't get at least one vehicle that is doing this. Just use two people. One to pull the cable release and the other to slap the hood with their hand and tell it to cooperate. Usually, just a little "jarring" with the cable pulled will get it to pop up.

mercedes a160 passenger window will not close

open the door and you will have to release the latch by doing it manually
either by going up or down
have a loock at your mabual if you have it
sometimes you may have to use some force but it is worth it
many times this happened to my bbot
if not than you will have to release panel as '' string'' may have broke or come up dislodged
by the way when doing manually try the handle on the outside as the same time to release latch

on what? the trunk, door hood?

There is a switch on your hood latch. They get damaged sometimes when the hood opens and closes. look down on the latch and you will see the sensor with an electrical plug. There are two 10mm bolts holding the latch in. remove them and the sensor is in the latch.

Can you open and lock your doors?
If yes, then it could be the boot catch.
Try a good mercedes scrapy for the second hand boot lock unit. Dronsfield mercedes are good, 01457871717