If you mean the Save G-Code button, I am having the same problem. I have been printing all day. One set of objects is long ~ 6 inches, but not wide. Prints OK.
Another object is 5.7 x 6 x 0.75 hi. This will not print. The Save G-Code button is grayed out. I fiddled with the CAD file, reconverted to .stl several times, reloaded the latest Cura. Nothing. The system works fine on smaller objects, and this one does not exceed the platform limit, so I am at a loss as to what the problem is.