What Happened to the Joint Comprehensive Plan of Action?

The chinese and the british signed this joint declaration in 19 84. It was supposed to be effective for 50 years. But then what happened? In 20 20, in 20 21, they went back on it. Have you heard of the j c p oa, the joint comprehensive plan of action, the iran nuclear deal that the americans signed in 20 15? They walked away from it. Whether it signed it or not doesn't matter. From a signed agreement, it' happened.