I have not read of anyone else posting who has these exact symptoms.

Symptoms:
-Key fob will NOT lock/unlock car when pressed by itself. LED blinks from remote. No corresponding LED light blinking from car.
-Key fob WILL unlock trunk. LED blinks from remote. Corresponding LED light blinking from car.
-Key fob WILL lock/unlock car if pressed right after pressing unlock trunk. LED blinks from remote after unlock trunk key pressed. Corresponding LED light blinking from car. Then LED blinks from remote after lock/unlock key pressed. Corresponding LED light blinking from car. And doors unlock or lock.
-If I want to lock or unlock right after,I have to press the trunk button first again.

Steps already taken:
-New battery in car and key fob.
-Key fob battery reset done (battery backwards for ten seconds).
-Key in ignition, ignition on, and un/lock button pressed for ten seconds.

Any help would be appreciated.

 

Just a couple of suggestions...

Have you tried with the ignition key off and out of the ignition switch disconnecting the vehicle battery then reconnecting it? With the battery disconnected press on the brake pedal to drain away any residual electrical power in the car's electrical system. Be sure to follow the correct steps for disconnecting and reconnecting the battery.

Have you checked for water in the cabin? Water drain blocked maybe? Check under the seats. Is the car's security module under the passenger seat like in other models? I don't recall. Anyhow check for dampness.

If the above don't help all I have to offer is then the car needs to visit the shop where someone with a Porsche diagnostics computer can query the car's security system to see if there are any error codes. If there are this might shed some light on what's wrong.