If it was working when parked a year ago, it cannot be too seriously jammed. I would forcefully rock it back and forth while using the manual shifter to get things loosened up.
Remove the battery cables from the terminals and clean those connections too. If the battery is more than 5 years old, get a new one.
Remove the battery cables from the terminals and clean those connections too. If the battery is more than 5 years old, get a new one.