H Kevin,
Is it clean 3.1.6 install or instance after upgrade?
In 3.1.4 we updated setup to use separated oxAuth client for IDP. As result here is no reference to `identity/logout` now.
Here is default IDP [config](https://github.com/GluuFederation/community-edition-setup/blob/version_3.1.6/templates/oxidp-config.json).
Here is IDP client [entry](https://github.com/GluuFederation/community-edition-setup/blob/version_3.1.6/templates/clients.ldif#L35).
Can you share `ou=oxidp,ou=configuration,inum=<applianceInum>,ou=appliances,o=gluu` oxConfApplication attribute value?