The root/intermediate certificate is expired. When certificates are revoked or expired then the same issue appears. An incorrect date and time on your PC is the reason for many errors that go on between your server and computer. The keychain is used at least one and possibly two ways in OS X when connecting to an SSL VPN: 1.
Method 1: Update/Check your date and time Mac OS X.
How to fix invalid certificate error mac Describes an issue that triggers a 'The name on the security certificate is invalid or does not match the name of the site' warning in Outlook in a dedicated or ITAR Office 365 environment.
