Why didn't guava ripen after being stored in the fridge?
From epicurious (I love their YouTube channel):

You can buy hard, green guavas and allow them to ripen at room temperature. Placing them in a paper bag with a banana or apple will allow them to ripen faster. Guavas may be treated with edible wax to delay the ripening process, so you may want to rinse them off to speed ripening.