I cannot find any tech info on this unit.
Here are your parts
Parts for W27400 - AppliancePartsPros.com

But the first thing I would check is the power to the unit.
Try flipping the breaker off/on slowly a couple times, sometimes you can loose half the line without actually tripping the breaker.
The heating elements require the full 240 volts.
If this does nothing, check the voltage at the plug
L1 to L2 should be 240 volts
L1 to Neutral and L2 to Neutral, both should be 120 volts.
If OK
Unplug the unit and check the wires at the terminal strip in the machine to make sure none are loose or burned out
If OK
Check the power at the terminal strip.
[COLOR="Red"]Be careful as 240 volts is lethal !!! [/COLOR]

If the power is good and since the unit stays in pre-heat then odds are high that the control board/timer is toast.
I would check the wiring just in case you have a burned off connector or some other wiring problem.
I cannot find a fuse or thermal cut-off in the parts that would stop power to the elements.

Here is what comers up for that error code.
I cannot confirm that it applies to your unit as I cannot find a tech sheet on it.
F5---Hardware and watchdog circuits disagree---Replace clock assembly (also called the ERC)