PID Autotuning not working – large initial overshoot, no oscillations
I recently experienced exactly the same problem. For me it was related to an incorrect heater cartridge. I accidentally used a 12&nbsp;V cartridge in a 24&nbsp;V powered system. 

The heater element got accidentally mixed up between the higher voltage parts container and I forgot to check the resistance. Inserting the correct voltage heater immediately fixed the problem, but it did require a retune of the hotend.