SOI gets disconnected from ServiceDesk which prevent it from creating tickets.
You will get this error message if you attempt to create a ticket manually "Connection to Help Desk has been lost and ticket creation has failed"
ServiceDesk 17.3 had a defect which close the SOI connection after an hour.
Release : 4.2
Component : Service Operations Insight (SOI) Manager
Customer needs to apply Rollup 4 for ServiceDesk 17.3