This is now your zone to take risks. Big or small. You might find some gold, and keep a good deal of it. You might end up tossing most of it in the bin. But either way, it’ll get you writing again, and you’re sure to learn more about your fictional world.
A few things I’ve tried: What if someone who originally died actually survived? What if someone else died instead? What if this character was removed from the story entirely? What if these two new people were romantically involved? What if the hero first meets the bad guys, but they’re pretending to be the good guys? What if the villain was redeemed? What if he only seemed to be redeemed, but tricked everyone?
Flip things around. Play with it, and have fun. Sometimes it might feel like you’re writing fanfic of your own story, but that can be very motivational. Imagine what kind of fanfiction your readers will write when you’re a famous author! That ought to get you moving again.
Have fun, and good luck!