When can I play volleyball again after a scaphoid fracture?

When the bone heals. Follow your doctors advice. Once the bone is healed he should release you back to activities as tolerated. This bone can be extrtemely variable in length of time to heal so listen to the advice of your doc before return to play.
It depends. Is your fracture healed? Usually, scaphoid fractures take anywhere from 8-12 weeks to heal. Was your fracture fixed surgically, or treated in a cast? Many factors go into return to play decisions after scaphoid fractures, but the number one question is "is the scaphoid healed?" and if the answer is yes, you should be able to resume volleyball.