https://www.ifixit.com/Answers/View/772715/Subaru+key+fob+not+working+after+battery+change
Subaru key fob not working after battery change - 2010-2014 Subaru Legacy - iFixit
I fixed this myself, but I'm just not in a state to type up the instructions. Hopefully someone gets some benefit. I (think) all Subaru key fobs from the 2010...
subaru key fobnot working