Cannot calibrate- Z axis problems  

Cannot calibrate- Z axis problems

Z axis errors on i3mks2
I was wondering if any other user had a problem with the i3 mks2 printer. One day it would not print. The unit somehow lost it's calibraiton . I am having problems with my pre assembled Prusa. It would not print. - would stay at the max Z height and not move down.The printer would not print. It would not find the Z=0 level. I ran the Z calibration unsuccessfullly. I then got an error that the printer lost it's preset factory settings. I then re-ran the XYZ calibration. The printer failed the XYZ calibration. I consulted the manual and checked that the X ,Y and Z axis all move freely and are correctly aligned. They all passed. I then re-ran the X,Y.,Z calibration

As Blas suggested, I checked the operation of the Z sendor in the calibration>show endstops menu. I was able to have the Z sensor detech a metallic object. It successfully changed state from 0 to 1 and back to 0 as I swiped the metal object by the sensor.

I also checked the positon and tension to the PINDA cable. There seemed to be no obstructions or excessive tension present.

I did notice that after doing Z calibration the gantry would not move downward. The Z position detected was 0 even though the gantry was at the max height from the base. The only way I was able to get the gantry to move downward was to go into the settings>Live adjust Z and change the zero to a negative number. After doing this I exited the menu and was able to do a calibration. It successfullhyh measured the nine reference points. It then searched the four bed calibration points. but failed at the third point and said that bad calibration point was not found.

I them moved the Z axis about half way upwards as suggested. The Z height measured at Z = + 68 mm.

Other than reloading the firmware and drivers, does anyone else have any troubleshooting ideas?

Thanks
Tom