Few more "won't start" scenarios I've hit that aren't on most checklists:
Servo-specific: the drive needs to complete its initialization sequence before the press will accept a start command. On Fanuc, this takes 8-15 seconds after control power-on. If someone hits the start button too fast after turning on the control, nothing happens and there's no alarm — the drive just isn't ready yet. The status display will show "bb" (base block) until it's ready. Yaskawa shows "Servo OFF" in the same situation.
Temperature lockout: some presses have a motor temperature interlock that prevents starting if the motor is too cold OR too hot. In winter, if the shop drops below 5C overnight, the motor winding resistance changes enough that the drive won't enable. We had this happen every Monday morning in January until we added a cabinet heater on a timer that kicks on at 5 AM.
Lubrication interlock: most servo presses won't start until the lube system has pressurized. If the lube pump runs but pressure doesn't build (clogged filter, air in the line, relief valve stuck open), the press sits there with no alarm on some HMI configurations. Check the lube pressure gauge directly — don't trust the HMI status alone.
The weirdest one I've seen: press wouldn't start, no alarms, everything checked out. Turned out a mouse had chewed through one wire in the 24V interlock daisy chain inside the cable tray. The wire was making intermittent contact — sometimes it worked, sometimes it didn't. Took 4 hours to find with a megger. Now we run the interlock wiring in metal conduit.