IIRC, you can get this message if you pick the wrong ID file for the certifier (e.g. OU cert).
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Now how did you set up an internet certifier? Either used 3rd party certifier like verisign/ RSA etc. Or using one of the two types of domino CA? Perhaps there is some kind of misconfiguration Or update error. Please navigate here for more help: https://www.ibm.com/support/knowledgecenter/en/SSKTMJ_9.0.1/admin/othr_settingupaninternetcertificateauthority_c.html