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.