Answer: Boy, that is strange. It sounds like you know what you're doing, so I can only speculate on some possible factors.
Beans need to absorb quite a lot of water before they'll germinate, so you need to keep the seedbed quite moist.
If you planted the beans too shallowly, it's possible that they sprouted but dried out and died.
On the other hand, if the soil is too wet, the seeds will rot.
It's possible that birds or other critters are pulling up the sprouts as soon as they appear. See if you can find the seeds in the soil.
You might try soaking the bean seeds overnight before planting. You can also check the germination rate of the seeds by placing several between two sheets of moist paper towels, and enclosing them in a loosely tied plastic bag. Keep the towels moist and place the bag in a warm spot, and the seeds should germinate in 3 or 4 days.
That's all I can think of. I hope this helps!
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