What's in your start gcode ?
Maybe you use a variable that has been deprecated between the 4.12 and 5.6, and is set to 0 ?

https://all3dp.com/2/cura-start-gcode-end-gcode/

For example :
{print_temperature} Alias for material_print_temperature (deprecated, do not use)
{print_bed_temperature} Alias for material_bed_temperature (deprecated, do not use)

instead of :
{material_print_temperature_layer_0} and {material_bed_temperature_layer_0}

http://files.fieldofview.com/cura/Replacement_Patterns.html

The way that the heaters turn on and off is by using a gcode command. So my first thought is that somehow the new slicing profile is not spitting out those commands. Try comparing the generated gcode from slicing the same model in both versions and see what’s different. The temperature commands have to be at the start so should be easy to find. The gcode commands themselves are very googleable.

For me, this problem started with Cura 5.6. 5.5 was OK. It stems from lines in the start.gcode that have patterns with two values inside the curly braces such as:

M104 S{material_print_temperature_layer_0, initial_extruder_nr} T{initial_extruder_nr} ; set left or right extruder temperature

For a temperature of 200 and extruder 0, this should produce the gcode "M104 S200 T0", but instead produces "M104 S(200,0) T0". The latter causes the nozzle heater to shut off.

It looks like this bug will be fixed in Cura 5.7. (https://github.com/Ultimaker/Cura/issues/17501)

So the solution is to either go to a Cura version older than 5.6, wait for 5.7 or edit the start.gcode. For me, if I remove ", initial_extruder_nr" from each two value pattern, it works OK. In my Flashforge Creator Pro start template, this pattern appears 4 times. My nozzle temperature line looks like:

M104 S{material_print_temperature_layer_0} T{initial_extruder_nr}

If you have a configuration where the individual nozzles temperature/settings are different from the global ones, then things may not work as expected. For example, I am not sure if replacing {nozzle_wipe_gcode, initial_extruder_nr} by {nozzle_wipe_gcode} does the right thing, particularly with the left extruder. But I am printing fine with the right extruder.

New Lemmy Post: Upgrading from Cura 4.12 to 5.6 no longer heats extruders or bed (https://lemmy.world/post/10337593)
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