Car Gurus: Intermittent Engine Trouble

My 2015 Ford Focus Hatchback (2.0 L Engine, I think) has an intermittent issue where the car won’t start. Starter solenoid doesn’t even click. Battery was 6 years old and just changed with brand new battery two days ago. Issue remains. Mechanic checked all the obvious (alternator, etc.) Where else should a mechanic look? Ths is an automatic transmission, if it matters…that variable speed design of which I forget the proper name. Feels like driving a manual transmission.

Go ahead…hit me with ideas!

If you need to do something like press on the brake to start the car, there’s a chance that the switch which indicates the brake is pressed isn’t working.

The brake switch which interlocks the starter usually also works the tail stop lights, so you can test the switch by working the brake pedal while looking at the brake lights (either reflected off another surface, or a helper saying when they see the lights turn on).

Also, the main ignition switch, especially if it’s one you use a key to turn.

Could be a faulty ignition coil. Battery cables could go also.

That was my first thought, a bad cable.

At the risk of stating the obvious… the starter?

Neutral safety switch.
Gear shift position alignment.
Brake interlock switch.
Ignition switch.

With the engine off, have someone stand in front of the car and look at the headlights. Turn on the headlights. Do they work? If they do not work, then that tells us something. If they do work, turn the key to the start position. Do the headlights stay on, or turn off, when the key is turned to the start position?

Crank position sensor (if it has one). Just spit-ballin’

Intermittent is the worst! Can’t find/fix it when its working, can’t trust to drive it when its randomly bricks.

On the cars I’ve had, a bad sensor will allow the engine to crank, but not start. The OP says it won’t even crank.