If you’ve had issues with bundt cakes sticking in the past, there’s a 99.9% chance it is your pan. There are an array of things (abrasive sponges, dishwashers, and more) that can damage the nonstick coating on your pan, making it easier for things to stick to it. Additionally, I've found that it's best to wait to grease the pan until just before you add the batter. You'll see that step noted in the recipe directions below, along with several other helpful specifics.