Wondering if anyone has thoughts on fixing a Sigelei 100W, which is powering up but not firing.

Things I've checked:

1) Batteries (two sets)
2) Atomiser (three tested)
3) Dismantle and check board (no evidence of issues)
4) Check board voltage
5) Check voltage at 510 (no atty attached)
- 3V falling to 0 (check atomiser)
6) Check voltage on atmoiser
- 0V
7) Replace pin
8) Clean

Tried the above, no joy.

Also, when firing the backlight comes on the screen, but no power to atomiser :-(

Any ideas welcomed.