Oh also misting with humidity domes on might be why the last beans you tried rotted.. Here is a simple method I use with near 100% rate with soil, soil is the easiest IMO to sprout seeds.
Soak bean in distilled water for 12 hours, the bean should sink, you might need to give it a poke with your finger, once it sinks its ready, I don't wait for a tap root.
Water soil until you see runoff then plant bean 1/2 in down and place dome over area, then forget about it, just a visual check to see if it sprouted daily.. No misting or anything..
It could be too much moisture under the surface of the soil, by not misting and having a dome on it the medium slowly dries and once it hits the right moisture content the bean sprouts. Its simple and effective. This is recreating what happens to wild seeds, Seed falls, soil gets wet, soil starts to dry, bean sprouts...