Why are my soaked dried beans crunchy?

I tried a recipe for refried black beans the other day. To avoid excessive sodium, I bought a bag of dried black beans and soaked them overnight - actually until mid-afternoon the next day. After draining/rinsing, I put them in new water in a pan and heated them to simmering, per the recipe instructions, and left them that way for at least 4 hours, probably closer to 5. The recipe suggested 1 1/2 hours, and that they’d turn to a paste. Well, mine were still beans after about 4 hours. By the 5th hour, they were a paste-like consistency, but when I put them in a different pan to mash (again, per the recipe), they were really hard. They sort of mashed, but they were crunchy. I threw them away. I still have 1/2 of the dried beans; I can try again. But is it worth it? My wife had the same issue one time trying to make baked beans from dried beans. What are we doing wrong? Thanks!