Lights blink with Key fab, but does not unlock or lock; engine acts locked out.

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The car does not seem to respond to my key fab or manually to the master key. The batteries in the key fab needed to be replaced for a while so I just used the key manually. Last night the car would not start and got stranded in a parking lot. The car acts like it is electronically locked out since it fires just fine. It only has 75k on it and it has been serviced and runs like a new car. This morning I went and replaced the fab batteries. After trying several times the car respond to the fab and locked;/unlocked doors and the car started right up. I drove home then the same problem started.....the lights blink on the car so I know it recognized the IR but the doors will not lock or unlock. I tried synchronizing. No change. Help!!!!1