Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
When a lens won't do Auto-Focusing, then either
1. it is an incompatible lens, not workable with the camera body in question, or
2. it has dirt on the contacts, in which case: clean by wiping the contacts, on both the lens mount of the lens and the lens mount of the camera, with a clean dry soft cloth. Wipe gently, lest you remove the sensitive coating on the contacts.
3. the lens may be 'broken', or the camera body may be defective... the easiest way to find out which one it is, is to try a different lens that is compatible with the camera body, and see whether it Auto-Focuses OK.
Let me know how it goes - I will have more suggestions to offer.