Sigma has discovered an issue with their lenses and the Nikon D5300. Sigma lenses with internal motors, do not function properly on the Nikon D5300. The Optical Stabilization (OS), and Live View Auto Focus functionality does not work correctly. This issue is specific to this lens and camera combination. On November 20th Sigma will release a firmware update to fix the issue. If you have a discontinued lens you have to contact an authorized Sigma distributor. If the Sigma lens is compatible with the Sigma USB Dock, the Sigma Optimization Pro Software can be used.
All future Sigma lenses will have the latest firmware.