A sin is a fault of yours that earns punishment, in this life, next life, after-life or somewhere else.
Free will is the ability for “You” to decide what “You” want to do.
If God, society, environment, fate compel you to act in a particular way, then it cannot be your fault. It can earn a negative consequence, but that can’t be a punishment. (A diabetic deprived of food by external agencies may still go into a coma, but it is not their fault, not a sin.)
