Hi Fabien,
single logout is a combination of service provider and identity provider handshake.
As in your case the user may click on a logout button/link on the service provider side,
then an SLO request is send to the IdP
IdP informs all service providers for which the user was logged in
and terminates the session.
In order to be able to judge why it is not behaving as expected in your scenario it is required to know the concrete application (or service provider) as well as the identity provider.
You stated that you have SAP netweaver and SAP ID provider. Could you explain a bit more concrete which applications you are referring to?
SAP netweaver is an ABAP on-premise application?
SAP ID prvider is SAP Single sign-on (on-premise) or SAP Cloud Identity (Cloud service)?
Best regards,
Marko Sommer