a few days ago my engine electronics light went off now my car won't start. All electronics work but nothing from engine. 1997 Mercedes Benz e420

Have you checked the fuses?

Yes fuses all look good

Will the engine turn over?

And today my key doesn't want to turn

No turn over. I hear a humming coming from the top of the motor from a round black thing. Looks like a strainer

Your key has chip in it?

You can try this,remove the key from car,then remove the positive cable from battery for about ten minutes,then place key in car and turn to the on position if you can,and then replace the battery cable,if it is a antitheft issue this will reset it.

Even if you cant turn key to on,do the steps anyway.Just place key back in car.

Ok my friend took the battery over night to make sure it had enough charge to start. I will do that first thing in the morning.

Thank you for your help I will let you know how this turnes out. It is my only vehicle

No it didn't work