When this error message is shown in Data Hub, then the privateKey must be generated using the DocuSign Portal and not with OpenSSL like described. Please read the Prerequisites chapter to fix this error.
When this error message is shown in Data Hub, then one of the parameters contains a faulty entry or the Activation URL which grants the permissions to the API user was not opened. Please check all parameters set in the Prerequisites chapter or see the Best Practice Configuration chapter to fix this problem.