There can be varying reasons as to why your jam didn't' set up properly. Your Strawberry Jam most likely needed to cook longer or there is a small chance that the strawberries didn’t have enough natural sugar for the jam to set. It’s a combination of cooking time, sugar, and lemon that makes this recipe gel. (Lemon acts as a natural pectin in this recipe.) If you followed the directions and it didn't set up properly, let the strawberry jam sit overnight in the fridge. If that step still doesn't get it to stiffen up and set, you can try re-cooking it for a bit longer and either 1. adding in a bit of pectin or 2. adding a bit more sugar and lemon (not much, just give it a taste test.) For best results though, I recommend using a thermometer and making sure your strawberry mixture reaches 220 degrees F. Another method to test if the jam is ready, is the “plate in the freezer” method. (Remove jam from heat while conducting the test.) Place a small plate in the freezer when you begin cooking the jam. When you are ready to test to see if the jam will set, remove the plate from the freezer and place a quarter size amount of the jam in the center of the plate. Place plate back in the freezer for about a minute. Run your finger through the jam on the plate. if it wrinkles and is jell-like the jam is ready. If the jam “fills in” the line you made with your finger, you should cook the jam for another few minutes.