How to fix a non-opening electric door on the passenger side of a Volkswagen Sharan after replacing the 12V battery

I thought the fix was so weird that I decided to write a blog post about it. Have you ever wondered why the electric door on the passenger side of the Volkswagen Sharan won't open after you've fitted a new battery? Neither had I until last week when I picked up my car from the mechanic and noticed that the door button was blinking, and nothing happened when I pressed it. The closing mechanism was…