Standard problem with these units is the NiCd cell battery.
If the battery is dead, the unit will not start at all.
Replace the battery with the same type and capacity.
The battery normally lasts around 10 years, so put a sticker on the 4195A and replace it in 5 years intervals!
I'm told that the battery contains calibration data. To not lose this data, make sure to power the battery pins on the PCB externally when replacing the battery.
If the 4195A battery is dead, it doesn't matter of course.
Even if one has no intention to use a dead 4195A, remove the battery. They leak and destroys the PCB.
The instrument works without the calibration data, but starts up a bit rough in performance.
I do not have the software, but please let me know if you find it!