WF Manager - WSU-GC/sharepoint-2013-docs GitHub Wiki
Trusted Security Token Issuer
When adding the WF manager you might need to update the trusted security token issuer.
New-SPTrustedSecurityTokenIssuer -Certificate $cert -Name <FriendlyName> -RegisteredIssuerName "00000005-0000-0000-c000-000000000000@*"