On a Windows Server 2012 R2 domain controller in our sandbox, logged in as the Domain Administrator, I attempted to seize all of the fsmo roles using the following PowerShell command:
Move-ADDirectoryServerOperationMasterRole -Identity “Target_DC_Name” –OperationMasterRole 0,1,2,3,4 -force
I successfully seized the PDC Emulator, RID Master, and Infrastructure Master roles, but the seizure of Schema Master failed with an Access is Denied message.
The Administrator account was a member of Schema Admins and Enterprise Admins, so it had the correct permissions assigned. After much online searching, I found the suggestion to make Schema Admins the primary group for the account. The default was Domain Users. After making Schema Admins the primary group, the PowerShell command worked to seize the Schema Master role.