According to the Inventables website, Carvey has a work area of 11.6" x 8" x 2.5":
Part of your design does extend beyond this 11.6" limit, it would seem. But how it didn’t get flagged up during the rough pass, I don’t know.
Easel Software lets XCarve owners set their machine parameters (work area bounds) in machine setup because the XCarve comes in several sizes (and some owners modify theirs to be unique sizes, as well). In the case of the Carvey, which is an enclosed system, you are restricted to 11.6" x 8" work area because that is all Carvey can reach. Even though you have stated your material is 12"x8", Carvey can’t reach part of it (if you look in the left panel, you can see the work area is the big white box with the gridlines in it, and your design does in fact extend outside of that big white box).