Can't rotate knob  

RE: Can't rotate knob

First check that the LCD cables on both sides (LCD board and Einsy board) are firmly plugged into their sockets. Maybe your problem is just a loose cable.

If you’re not lucky and the issue remains, then try wiggling sideways (softly) the knob, or pull it upwards just a bit while you rotate the wheel, to see if the scrolling function works, albeit intermittently.  

If the cables are OK, the rotary encoder might be defective; maybe a loose solder joint or a faulty internal contact.

On any case, I’d contact Prusa support via chat. They will be able to locate the exact source of the problem. If the rotary encoder failed and your printer is still in warranty, you should be entitled to a free new LCD board.

RE: Can't rotate knob

+1 for checking the cables. Loose or disconnected cables are often the common culprit of many minor issues in the computing world. Though this behavior is very odd and it is unlikely a cable wiggled loose unless you had a lot of weird vibration, or maybe it got tugged on during the electronic portion of the MMU2 upgrade.

RE: Can't rotate knob

HI

I have deleted your post from Prusa MINI, I hope you don´t mind.

Iwould suggest

1. Do a factory reset

if this does not help

2.Try to reload the Printer firmware

3. If you have very old MK3 it could be the knob issue, but I dod not asume, it will start not to work suddenly - it goes with some degradation, skipping some steps, before it stops forever.