This was a translation construction from parts. "'s" was given as a component but "Ivan's not working on this project" was marked wrong. It would not permit the contraction, common in most English speaking countries. It wanted "Ivan is not..."
Hi, as a native English speaker, I we would normally say you work 'on a project' and I don't usually hear someone working 'in a project'. So although it would be understood what you mean, it isn't how it would be said.