3791071 - Qualtrics Email Survey integration fails with error "404 Unable to find person by uniqueId"

The Qualtrics Email Survey integration fails and, when checking Execution Manager → Integration Center, the following error message is displayed:

Http Error response code 404 with response state text: Not Found while calling url:
https://<QualtricsDataCenter>.qualtrics.com/API/v3/successfactors/projects/<ProjectID>/evaluators ; Click text to download

When downloading the execution report, the following error is displayed:

{"meta":{"requestId":"<RequestID>","httpStatus":"404 - Not Found","error":{"errorCode":"PPE_5","errorMessage":"404 Unable to find person by uniqueId: <UniqueId>"}}}

SAP SuccessFactors HCM Suite

Error, response code 404, Integration Center, Qualtrics, Email Survey, Unique ID, User ID, Not found, PPE_5, 404 Unable to find person by uniqueId , KBA , LOD-SF-PLT-QLT , Qualtrics Integration , Problem