Many automatic transmission cars have a shift lock detent to prevent the vehicle being taken out of Park until the brake pedal is depressed with the ignition key on. A signal goes from the brake light switch to the shift lock module. Check that the brake lights work first. Most vehicles have a way to get the vehicle out of Park in case the battery has gone dead or the shift lock detent solenoid or module fails.
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Check fuse #6 (5 Amp) and fuse # 13 (15 Amp) in the fuse box.