SAML Troubleshooting Checklist
You can find your SAML test URL by editing the Single Sign-on Endpoint. See here.
Copy and paste the URL into a new Incognito browser window to test signing in.
If clicking on the SAML test URL does not take you to the correct login screen you will need to update your Remote Login URL to point to your Identity Provider. You can update your Remote Login URL by editing the Single Sign-on endpoint. See here for how to get there.