Hello
Lately, a person participated willingly in training videos, with the understanding that the videos were going to be sold. Few years later when we are finally in a position to market and sell the training videos the person is not signing a release form. Also, I am sole owner of said training videos. Can i still sell the videos? Can I sue them for not allowing me to sell the videos? Any advice would be greatly appreciated.
thank you.

You may be able to market the videos under an implied release since they appeared in the videos. Information is needed to give a good legal opinion on this matter.