PID autotune problem

Hi all,

I've been struggling with this autotune issue that I have with my delta printer. Kinda finished with the build and wanted to setup the PID values for the hotend, but when I send M303 E0 S200 C8, it timeout right away:

PID Autotune start
PID Autotune failed! timeout

When I manually set hotend to whatever temperature, it will heat up fine, just won't run the PID autotune. How should I troubleshoot this?
I'm running marlin on ramps 1.4