MK2 with MMU problems 🙁  

RE: MK2 with MMU problems 🙁

your heater block is assembled incorrectly. for starters,

https://help.prusa3d.com/wp-content/uploads/2021/05/Original-Prusa-i3-MK2S-to-MMU1.pdf
chances are that you are also using the printer with wrong slicer settings

Are you using the Prusa Mk2 MMU1 slicer settings? 
Do you have the Mk2 MMU1 Firmware loaded? 

First of all, I would remove the fan shroud, and loosen the extruder front housing, 

If neccessary I would cut the cable ties on the wiring bundle to the rear of the extruder and I would re position the heater block so that the long section of the heater block runs front to back with the heater wires and the thermistor wires along the left hand side of the heater block (Looking from the front

then I would tighten the extruder housing, re arrange the wiring bundle as described in the assembly manual, (linked above) making sure that the cable tie nuts, are located in the correct positions
Then I would replace the fan shroud. 

next I would turn the printer on, and preheat to the preferred temperature, 
while this is heating I would press the display knob once  and rotate the knob until you can see the firmware version (I believe it is in the last LCD Menu option)

 You should be able to download  firmware from here if needed      https://help.prusa3d.com/downloads

If the firmware is OK, 
I would check that there is NO filament loaded. 

If there is filament loaded, I would start by unloading all filament

then I would check the first three feet of each filament for damage,   the extruder gears can chew up the filament if it is not feeding properly

If there is any damage, cut the filament back to good filament. 
then cut the end of the filament at an angle as normal. 

Choose a colour for extruder 1 (in the enclosed files, I have nominated black) select load filament 1 on the LCD Display

the filament is usually pushed up a length of feed PTFE tubing and into the extruder ( extruder 1 should be 'Ticking' at this stage. )

as you feed the filament into the extruder the extruder should grab the end of the filament. at this stage, press the lcd knob... the extruder should feed the filament quickly, into the top of the X carriage assemble, and 'Park it' about 20 mm inside the X carriag assembly (At this stage the filament IS NOT loaded to the extruder)
Repeat the process with a contrasting colour filament in extruder 2, and the second filament should be parked about 20mm into the X carriage assembly.

Now  unzip the files that I have attached below, and transfer the Gcode onto your SD Card
Insert the SD Card into the LCD and select 'Print from SD Card' then select "JorisTag.Gcode"

the printer should heat up with the bed at 70C and the nozzle at 215C, then it should start printing

the printer should initially try to print filament 2 (this should purge whatever colour was in the printer before so it may appear the wrong colour! (don't worry))
then the printer should change filaments to filament 1, and print a larger purge line, (As shown on the image below )(Note this larger purge line will probably start with the colour from filament 2... as it is purged from the nozzle, again, don't worry. )

After printing all of the colours used in the print, (2 colours in this case) the printer should stop, awaiting your attention... (This is to allow you to remove the purge lines, if they a re likely to interfere with your print... In this case, they will not interfere, so just press the LCD Knob) (Be aware that if you do not respond, the printer will wait a while, then begin the print anyway. )

the printer should now begin the print and change filaments automatically. 

regards Joan