Green “wanted to do it … and he did do it,” Williams told
"But the ... how do I say this diplomatically? The powers that be at the time did not see it fit for him," Williams said. "Some folks on his team just felt that the priority should be on his album at the time, so they elected not to [release] that song."
When Williams' own version came out, initially as part of the soundtrack from "Despicable Me 2," Williams said: "He was totally down with it. He was one of the most gracious people when [my version] came out."
Here's Williams' interview on "The Howard Stern Show":