Would that be the “Deformation Setup” button or the “Build Rig” button? Build rig should take you to a UI that lets you input a name for the character and choose a project. After that, it will want you to create a thumbnail for the character. Once those are done, it will begin the build, by opening a new scene, referencing in the export file, and then building the rig. At which point in that process is it crashing? Any details, images, or files you can provide would certainly help.