If immediately after installing WordPress on a site you receive a 404 when using SSO, please check:
OpenLiteSpeed
The WordPress SSO relies on the WordPress .htaccess being in place. OpenLiteSpeed so it doesn’t auto-reload .htaccess files meaning some tools including SSO won’t work immediately after installation. Please wait 24 hours or consider upgrading to LiteSpeed Enterprise.
Nginx
If your server is running Nginx, ensure you have the necessary rewrite rule: Configure Nginx for WordPress Permalinks
