Problem with Marlin 2.0.5.3 / BLTouch upgrade with Sovol SV01
I think I might have found it - PID problem (heater has a PID loop). Standard values are 32/3/85 (P/I/D). Just watching the temperature, I noticed there was a lot of overshoot.
It appears that to continue after a temp wait, it must stay within some limit for a period - don't know either number. But, presumably, it wasn't.
There is an autotune PID gcode - M303 E0 S200 C8 says 'autotune extruder 0, at 200 °V, looping 8 times. Ran that and I could see it getting better on each iteration. Unfortunately, didn't manage to find a way of seeing what it came up with, and could not get the result written back to E2P either (M500).
So, resorted to tried and trusted techniques - fiddled with it. In the end reduced P to 20.0 and I to 2.0 - and it started printing.