The RPS certificate for Skype for Business Online, Administration Center could not be loaded.
RPS certificate is expired or there are incorrect certificates in the certificate folder.
1. Check the certificate folder [Windows Live ID Server installed folder]\config\CERTS (default path 'C:\Program Files\Microsoft Passport RPS\config\CERTS') and make sure there is only one valid certificate. Expired or invalid certificate should not be placed in this folder.%n2. The certificate with private key should be installed in local machine store.