Got lazy but have posted once about my Extruder being the reason why Octoprint or Firmware is not starting the Print.
I compiled my Marlin Firmware by adding
#define DEFAULT_Kp 16.44
#define DEFAULT_Ki 1.58
#define DEFAULT_Kd 42.75
and it starts, but it does weirdly extrude. When I hit "Extrude 5mm" Manually while nothing is running then it seems like a nice constant flow, but when Printing it somehow stocks, retracts or smth when trying to print. At first I thought its TPU and a new abstract material I have never touched but this currently is the good old Black PLA from Creality that I always used.
I use Cura and just used the default settings for PLA like always.
You'll need to determine that extruder value yourself by marking out 70mm of filament from the top of the nozzle and then slowly extruding out 50mm of filament. You should have 20mm remaining after (measuring all this with digital calipers). If you have more than 20mm, you're underextruding and less means over extrusion. To determine your new extrusion value, multiply your current extrusion value by (actual extruded amount/requested extruded amount). For example if you have 30mm leftover, it'd be 420.69 * (40mm/50mm) = 336.552