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 available, run Powershell with Windows Azure/Office 365 Cmdlets.
Connect to Office 365
$LiveCred = Get-Credential Connect-MsolService -Credentials $LiveCred Set-MsolADFSContext -Computer <Incert your ADFS Server name> Convert-MSOLDomainToStandard -DomainName <Incert your federated domain name.com> -SkipUserConversion $true/$false -PasswordFile C:UsersPassword.txt
$true will skip converting all users at the same domain to Standard users.
$false will convert all users at the same domain to Standard users.
If you only need some users, you can use value $true and convert the users you need to access Office 365 one by one.
All users converted back to Standard users will need a temporary password and a list will be generated to distribute to your users.