I don't know about manual tranny, but do know about auto.

Symptoms sound like fraying and finally torn wire on the way to the solenoid.

It ususally wears and breaks right after it goes down out the front of the plastic-covered shift lever housing, into the tranny tunnel. Breaks inside the tunnel, on passenger side, giving you just a few inches of wire to work with.

If wire is broken, no amount of replaced relays or solenoids will help you.

Skinny under there and have a look. Or get it on a lift with a cooperative shop, that makes it much easier to find the wire if you don't know where.

It goes out the shift lever box, down into tunnel, forward along passenger side of tranny, over top of tranny somehow/somewhere, then rearward along driver's side of tranny to the solenoid.

If confirmed broken:
Take cover from shift lever housing, slide to one side.
Find wire going out grommet at front of metal shift lever box.
Pull broken wire up into pass. compartment.
Splice on about 1 foot good wire.
Push about 6 inches of wire forwards out thru grommet.
Use needle-nose pliers and patience for that, or a 5-year-old kid helper.
(DON'T remove grommet, you'll never get it back in)
Skiny back under and pull some more wire as needed out of grommet.
Splice to wire in tunnel, leading to solenoid.
Cover and protect exterior splice as well as you can.
Vaccuum tubing for protection maybe?
OK to leave the wire a bit longer than needed, with the extra in the box.
That way, if it breaks again, no splicing will be needed up above - just pull some more down into the tranny tunnel.