The project seems to have been saved with the Spine 3.7 beta, but you are using Spine 3.6
In any case, you typically can't reliably open projects from newer versions using older versions.
You could load Spine 3.7, export the json, then load 3.6 json and import it there.
You lose some data by doing this (particularly some extra information in meshes), but it the resulting project should be generally usable.
