Have you converted your domain to a federated domain before your Single Sign-On is ready?
This will make your users unable to login to Office 365.
If your ADFS Service is unavailable, run Powershell with Windows Azure/Office 365 Cmdlets from any computer or server.
Connect to Office 365
$LiveCred = Get-Credential Connect-MsolService -Credentials $LiveCred Set-MSOLDomainAuthentication -Authentication Managed -DomainName <incert your federated domain.com> Convert-MSOLFederatedUser -UserPrincipalName <incert your users username>
You will then reset your authentication method to Standard and convert your user from FederatedUser.