Two questions:
I have a 2000 Mercury Sable fully loaded;

1) My driver side door will not open or unlock with the keyless entry or remote. I tried to manually open the door with the key and it will not unlock... what is the problem and how can I fix it?

2) The power locks in the car will make the noise as to lock or unlock... but the doors do not lock or unlock how can this problem be fixed?

It could be a number of things:

. Test all under hood and under dash fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-3.html#post252145

Focus on Fuse #4, Power Locks Fuse (30A), and Fuse #22 (5A), in the U/H fuse/relay box.

. Check the Driver's Unlock Relay, in the U/H fuse/relay box. Disconnect the negative battery cable and remove the relay and clean the contacts. If necessary, replace the relay.

. Clean and spray the door locking mechanism with WD-40, if you can.

. Check/replace the left front door lock connections and motor, if you can.

. Spray the remote's keys with WD-40.

. Replace the remote's battery.

You may be hearing the all door lock/unlock relays but not the left front door lock motor--I don't know. Check all connections from this relay to the left door motor. Due to the anti-theft system, you may have to take the car to Mercury for diagnosis. These are very involved systems.