Answer: That's frustrating! Without more detail on your conditions, it's hard to pinpoint what happened, but here are some possibilities. Was the soil consistently moist? Once a seed breaks dormancy, it needs constant soil moisture. Even a short period of dryness can kill it off if it's just getting going. Soil temperature and oxygen supply are also important.
What about birds? They love seedlings, especially fat juicy bean seedlings. They can swoop in an devour everything in minutes. Some other common problems with seeds are sowing too deeply (a general rule of thumb is 2 or 3 times the seed's diameter) or having a "crusty" soil top that is hard to break. Damping off disease is a fungal problem that can strike. It causes stems to rot and seedlings to tip over at the base. It can also prevent seeds from germinating. However, damping off is more common when sowing seeds indoors using non-sterile mediums and containers. Finally, seed companies rigorously test germination rates, so it would be most unlikely that an entire pack of seeds was bad. I hope this info helps.
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