Error message is displayed after upgrading when certificate management feature is enabled

The following warning message is displayed after upgrading to HPE OneView 4.0 or later when the certificate management feature is available:
The current appliance certificate was first generated with an earlier version of the appliance. It does not support communicating with iLOs configured for two-factor authentication. iLO two-factor authentication requires that the appliance certificate include the 'Client Authentication' attribute in its Enhanced Key Usage field.

This alert can be ignored in environments not using iLO two-factor authentication. If you do plan to use iLO two-factor authentication simply generate a new appliance self-signed certificate or perform a new certificate signing request.
Solution 1

Client authentication attribute is missing from the appliance web server certificate.

Generate a new appliance self-signed certificate.
Solution 2
In case of a CA-signed appliance certificate, create a new certificate signing request.
Certificate management in the HPE OneView User Guide provides details.