Was this your first try after giving up shampoo? Agree it could be build up. I use rye, usually 2x a week, and sometimes it needs a vinegar rinse. Give that a try. Always a final cold rinse too. Have patience and experiment. I have fine normal hair and I hear results vary with curly or oily hair. It definitely takes time to find what works for you!
If you find it a bit hard to rinse all the rye out, combing your hair with s shampoo brush during rinse really helps.