No leaf development sounds like the stumps that slugs and snails leave behind, once they have feasted on just sprouted beans. Mice and pigeons also do great damage to seedling beans and probably other creatures in your area as well.

Your temperatures are warm enough for beans to sprout, if it wasn't we would not be able to sprout beans here in Britain at all.

I think you have two unknown quantities. Firstly, is the seed viable? Secondly, what is reducing my beans to stumps and how can I overcome that? I have never heard of a disease problem preventing leaf development.

What works for me is sowing beans indoors, preferably in small individual pots, cell trays or newspaper pots. They can go in anyway, eyes up or down makes no difference. Starting your seeds under controlled conditions should determine whether your seeds germinate or not. When you have grown your plants to the two real leaves stage, transplant them and protect them. In areas that are not too hot you can protect each individual plant with a plastic cola bottle with bottom cut off, pushed into the ground and the cap taken off.

If you don't want to start the seedlings indoors, you can do a germination test. Take 10 beans, place them onto a wetted sheet of kitchen towel, fold over and place inside a ziplock bag in a warm place, but not in direct sun heat. From day 3 onwards check every day to see how many have germinated.

Some people deliberately pre-sprout seeds as you do for a germination test, then very carefully transplant the seeds when the root is showing, and cover with only a thin layer of fine soil.

Wish you better luck with your next batch

Yes, I could use some luck here. I must say I'm not used to having seeds not grow when I plant them. This time I planted a test area that I can dig up a bean every now and then to see how things are going. If it doesn't work this time, I'll try sprouting them indoors.