Possible causes include but are not limited to:
Gear or pulley not secured to shaft (If it uses a grubscrew, that may be loose)
Gear stripped or otherwise damaged or pulley broken
Broken drive belt
Once you have an idea what is wrong, you MAY be able to get more advice and possibly spares here:
http://www.body--sculpture.com/index.php?action=contact
Broken shaft
Just THINK, February 2017