If the chain simply came off you need the part that connects the two pieces. Or the part came out of the light. Not sure if your question. They sell replacement switches and parts to do this from Homedepot or Lowe’s. Most hardware stores have them just make sure the electric is off.
Dismantle it while it's off the electrical socket. Find the problem. Fix it. Or tell us what's the problem, then we tell you how to fix it.
May need to replace the switch.
If the chain simply came off you need the part that connects the two pieces. Or the part came out of the light. Not sure if your question. They sell replacement switches and parts to do this from Homedepot or Lowe’s. Most hardware stores have them just make sure the electric is off.
exchange that for a regular light. The switch breaks a lot!!