Check if you can still send commands like M115 and see response in log. It might be that firmware is stuck waiting for target temperature which would be a classic startup problem when printer is not configured correctly. You must reach target temperatur ebefore print continues so if it stays 2-3°C below it will not start.
"proceeds to print, but just on the firmware, while the printer is doing nothing" So are you now printing a gcode or not? That is a contradiction to me.Setting temperature in manual control uses different commands that return immediately so that is no test.
Great it is working now.