The process of Skinner's operant conditioning experiements relied on keeping his pigeons under fed so that food could be "an automatic reward." While he did not starve them, he kept them in a neurological state that activated survival insitincts. I see this as a flaw in his experiments, and he cannot appropriately conclude that they lack free will. He can conclude that the pigeons will reliably do what is easy and necessary to survive. What would the pigeons do if they had enough food? 

Maslow's Hierachy, which was taken from the Ayurveda Chakra system, states that we do not have access to self-actualization (free will) unless we meet our physiological and safety needs. Because the physiological needs of the pigeons were not met in this experiment, it is not an appropriate measure of self-actualization if we consider Ayurvedic research and Maslow's findings. 

I think we do not have free will unless our physiological, safety, belongingness and esteem needs are satisfied. I think that Skinner overlooked the complexity of the psychological and physical needs of the human experience when he concluded that we do not have free will. 

Although, I think he accurately asseses that we sometimes innapropriately measure what things are of our own free will, and what things are curated for us externally. For example, a child from a wealthy family who did not have to work for their money may innapropriately assess that their success is the outcome of their will power, when it is more accurately the outcome of their parents externally curating that for them. 

Skinner, B.F. 1968. The Technology of Teaching. New York: Meredith Corporation. pp. 61–2, 64–5, 155–8, 167–8.

Diane Roberts, 2018. Maslow's Hierarchy vs. the 7 Chakras: Interestingly Similar: Psychology Today.