V3 should be supported in Cocos Studio - the format is quite old. But we’ve recently added optional enhancements to for format to support polygon packed sprite sheets. These might cause trouble in Cocos Studio’s loader code.
Try to deactivate polygon packing & polygon trimming if you’ve enabled that. This might already solve the issues. If not change the “Data Format” in TexturePacker to “cocos2d v2 (old)”.