Have the client verify that the user the API Key was generated under has org admin permissions (with cog access enabled) and that the user is active in the PI Software. If the user has been disabled, a new API Key will need to be generated under a different user
Check if the candidate applied for a job with the company previously. If so, verify that the integration is updating the job prior to pulling the candidate insights packet. An example of how to update the job can be found in the Integrations Example section of this site.