SAML Logout button not working


I’m trying to configure SAML with Okta as IdP Provider, but when I configured it the logout button on top right disappeared until I configure SLO Requests.

With SLO Requests configured, logout button is here but sign out not working, in fact when I’m clicking on logout button, it immediately sign in again me.

In addition, I have not error logs on solutions (nextcloud, nginx or okta).

Is that possible to have logout button without SLO Requests ?

And about SLO Requests not working, any idea please ? Maybe I missed someting…
Thank you for your help.