In order to diagnose the problem you are going to need a test light or a volt meter.
You will want to access the connector at the switch and check for 12 volts at the Dark Green wire. If you do not have power at that wire, then you need to check the 40 amp fuse at position 104 in the battery junction box.
If the fuse is okay, then you have an open circuit between the battery junction box and the seat.
If you have power at the seat switch, then check the ground. Take the test light and connect the end to the power circuit and probe the black wire at the seat. If the light lights up then ground is okay.
If you have power at the seat switch and ground is okay, then you will need to test the switch. Using the test light and probing the switch, you are looking for power going through each of the switches. For expample if you press the forward button, you should have 12 volts at the yellow wire with the white stripe. If the seat switch passes, you will need to replace the power seat frame.
If you do not have the equipment, I would recommend allowing a shop to diagnose the vehicle.