According to Il Sole Ore 24, Yonghong Li's decision to change the terms of the deal broke down the negotiations. As added by MilanNews, this is the second time that Yonghong Li has changed the terms, which has outraged Rocco Commisso. It's likely that Yonghong Li's plan is to start a bidding war, although Commisso has made it clear he won't participate in one. 

Now, the Ricketts family are back in the race and they could reportedly present their offer very soon. Commisso was convinced that he would be able to revive the greatness of AC Milan, investing in the transfer market while potentially building a new stadium. 

For Milan, Yonghong Li's refusal certainly won't do good in their dispute with UEFA, as more questions have been raised. Most likely, the club has lost its opportunity to use a new shareholder as an argument against UEFA.