Hello, I turned my printer on and off and started getting this error. First it says “printer is not ready,” and then I get an MCU error. There is no problem with my cable. I don’t think my printer is only one year old and has a hardware malfunction.
I would try rebooting your SBC (usually a Raspberry Pi) with sudo reboot (or through Mainsail). If that doesn’t work, I would take a look at the below article:
Also, could you please explain your setup more? Particularly, what SBC are you using?