First layer calibration - the nozzle is too high, and trying to lower it doesn't work (adjusting the Z axis has no effect)
I've been using the printer successfully for about 5 months, but recently I started getting prints to fail because the filament was not sticking properly to the plate. I noticed that the nozzle is now too high, so I tried adjusting it by going through the first layer calibration menu.
Everything appears to work ok, but adjusting the value up or down has not effect at all (the height of the nozzle doesn't change -- neither up or down, even though the display shows the numbers going up and down), so now I can't use the printer because all prints fail right away (the filament easily comes off the plate).
I tried installing the latest firmware and didn't help. I check that the PINDA height is still the same (about 1.5mm) as when things were working ok.
Any ideas?
RE: First layer calibration - the nozzle is too high, and trying to lower it doesn't work (adjusting the Z axis has no effect)
How do you know the nozzle is not moving? Try printing a calibration strip such as https://www.prusaprinters.org/prints/105404 and post a picture. I can't imagine why the live z calibration would not make the nozzle change.
RE: First layer calibration - the nozzle is too high, and trying to lower it doesn't work (adjusting the Z axis has no effect)
Is it possible that your nozzle is just so high that you can't tell the difference that the adjustment is making? You may want to follow the guide to adjust the position of your sensor:
https://help.prusa3d.com/guide/height-adjustment-of-m-i-n-d-a-superpinda-sensor-mini-_1545
I believe the distance is right, about 1.5mm
RE:
I tried adjusting the height while this is being printed and nothing happens.... I can't get the filament to stick to the plate. 
RE: First layer calibration - the nozzle is too high, and trying to lower it doesn't work (adjusting the Z axis has no effect)
If the pinda is too close to bed you can't adjust properly (max being -2000)
Follow the pinda calibration guide
https://help.prusa3d.com/guide/height-adjustment-of-m-i-n-d-a-superpinda-sensor-mini-_154547
To me that picture looks very close but hard to tell from pictures
RE: First layer calibration - the nozzle is too high, and trying to lower it doesn't work (adjusting the Z axis has no effect)
I don't know if you sorted your problem or not as it's an old thread but looking at your pictures the M.I.N.D.A looks to be a little high in my opinion.
The ideal height of the M.I.N.D.A should be 0.8mm. To make it easier for you to adjust without guessing, use 8 standard sheets of paper to adjust the M.I.N.D.A from the bed while the nozzle is touching the bed. BTW, one standard sheet of paper is 0.1mm.
Or you can use Prusa's directions of using the tip of a zip tie or a credit card as they both are also standard sizes of around 0.8mm. The reason I say to use paper is that everyone has access to plain old paper but not everyone has zip ties laying around or even a credit card, think children etc.