Post Upgrade
So 4s to core one… says needs fw but won’t take core one. Factory reset.. won’t take core one but does take 4s. After flashing says needs fw update and both say wrong hardware. Tried multiple drives, browser downloads and out of ideas
RE: Post Upgrade
Did you upgrade to firmware 6.2.4 or newer before you took the MK4S apart, as required in the build instructions? https://help.prusa3d.com/guide/1b-mk4s-inspection_207221#886859
If you skipped that step, I think you can still do it now, with the Core One assembled. But you will need to disconnect the door sensor before installing 6.2.4 (which is how the firmware distinguishes a Core One from an MK4s). After installing 6.2.4, reconnect the door sensor, then install 6.3.x for the Core One.
RE: Post Upgrade
Yes, and verified. Initially after the upgrade it asked for the firmware upgrade.. wouldn’t take core one, wouldn’t take 6.2.4 so I did a factory reset. Then it wanted a stick with firmware. Still wouldn’t take core one, did take MK4S but then gets stuck saying I need an upgrade and no further
RE: Post Upgrade
So another 6.2.4 upgrade was accepted and installed on the fully assembled Core One? In my understanding that should not be the case, since the 6.2.4 version is only meant to get an MK4S ready for the conversion. Any chance the door sensor is not properly connected?
RE: Post Upgrade
Ok we have got the program to take but now will not heat the nozzle. Have replaced most of these parts but no change. 
IMG_4941
RE:
Ok we have got the program to take but now will not heat the nozzle. Have replaced most of these parts but no change.
IMG_4941
Would check that the love board cables are plugged into the correct sockets. The thermistor cable plugs into the top most white socket outlined in green here. And ensure the black heater cable is plugged into the black socket above it. You can get cheap replacement on Amazon which work fine. For example: 24V 40W Heater Cartridge 104NT 100K Thermistor
RE: Post Upgrade
Yes, and verified. Initially after the upgrade it asked for the firmware upgrade.. wouldn’t take core one, wouldn’t take 6.2.4 so I did a factory reset. Then it wanted a stick with firmware. Still wouldn’t take core one, did take MK4S but then gets stuck saying I need an upgrade and no further
I had a similar problems. First the USB stick wasn't recognized. Turned out to be that the Prusa provided thumb drive was bad. I loaded the MK4 6.2.4 firmware onto a cheap FAT formatted memory stick and it was recognized but it wouldn't allow me to install it since it's for the MK4. So by unplugging the door sensor cable the firmware then sees the printer as a MK4. After that completed I plugged the door sensor back in and attached the USB containing the Core One firmware which then installed and I printed my benchy successfully.