Hi Linda, I'm sorry the fudge didn't set. It probably did not cook long enough. I am not a big fan of the microwave so I do it in the non-stick saucepan. You could try taking you fudge and putting it back in a no-stick saucepan with a teaspoon of butter (medium heat). Stir constantly until the mixture starts coming away from bottom and sides of the saucepan as you do in the recipe for Brigadeiro, the Brazilian bonbon. Anything cooked with condensed milk needs to be well cooked to set properly. I do hope this recommendation solves your problem.
Hi Dana
I found this recipe for fudge in a bag Let us know how it turns out
https://kidsactivitiesblog.com/79853/ziploc-fudge-in-a-baggie/