I'll offer a second vote for broken wires in/near the driver's side tailgate hinge.

I fixed mine by cutting open the sheath, finding the broken wires and soldering in repair segments, followed by shrink wrapping the joints and taping up the sheath. The harnesses are quite expensive for a bunch of wires (aftermarket harnesses for my old 240 were about 10x cheaper!), and I always seem to break clips whenever I have to remove the tailgate panel. It isn't a hard job-- I can do a repair in about an hour.

My rear wiper was seized up at the shaft. I got it moving again using penetrating oil. I turn it on briefly periodically now, which seems to keep it from seizing up again.

Good luck!

It won't let me edit. Did you try lifting the black flap and using the key to lock/unlock the liftgate? Don't break the key if it is reluctant to move, my 1998 key tumbler finally died due to salt.

Three problems. The wiper and lock could be because of a broken wire in the harness that runs through the tailgate hinge.

The washer motor not pushing out fluid could be because of a bad piece of tubing or plugged nozzle. Fix this last.

You will want to remove the plastic trim for the wire harness first and check the wire bundle. If that looks OK, then the panel must come off the tailgate so you can check the lock and wiper for electricity.

It is also possible that the wiper shaft that goes through the liftgate is frozen in place due to salt. Then, it will need to be greased and worked until clean and easy to move.