When a user is trying to create a candidate application using ODATA for a requisition which is posted privately (internal or external), an error comes up saying - "Job requisition not posted or already expired".
After the b1608 release of SF, it was identified as a defect that users are unable to create applications for privately posted job requisitions using ODATA API.
Firstly, you should check if the requisition for which you are creating a candidate application via OData API, is a posted requisition or not.
However, after SF release b1608, it was identified that some users are seeing this error when they are creating candidate applications for privately posted job requisitions using ODATA API. For such scenarios we have come up with a fix already and this fix will be rolled out in SF release b1702.
KBA , LOD-SF-RCM-API , Webservices & APIs , Problem