Hi Jean,
I'd like to confirm if the third party SSL certificate or token-signing certificate is expiring. If the token-signing certificate will be expired, please renew the token-signing certificate referring to the Resolution 2 in this link: http://support.microsoft.com/kb/2383983.
Moreover, we have a Federation Metadata Update Tool available. This update tool will automatically update the Office 365 service using Update-MsolFederatedDomain cmdlet when the ADFS token signing certificate renews on an annual basis.
You can get more detailed information about this tool from this link: http://blogs.technet.com/b/educloud/archive/2012/10/02/federation-metadata-update-tool-should-be-installed-with-every-adfs-and-office-365-deployment.aspx.
Thanks,
Edward Qu