Why do front-end users see the error message "URL No Longer Exists" when attempting to login to Soapbox using their Salesforce credentials?

If front-end users see the error message "URL No Longer Exists" when clicking the Login link in Soapbox that sends them to Salesforce to enter their Salesforce credentials, this may be because Salesforce has ceased to support https://*.secure.force.com URLs.

To resolve this:

1. Login to your Salesforce instance
2. Go to Setup
3. Go to Connected Apps > Manage Connected Apps
4. Open the Connected App you created initially to facilitate single sign-on through Soapbox
5. On the detail view of your Connected App, locate the SP-Initiated Redirect Endpoint for the Community (e.g., Experience Cloud) site
6. Copy this URL
7. Login to your Soapbox Engage administrator
8. Click on the App Launcher icon in the upper-left, search for Single Sign-On, and click on it
9. On the Service Provider Setup tab, locate the Front-end SAML Login URL parameter
10. Confirm if the current value contains a https://*.secure.force.com URL and that it is different from the value you copied from Salesforce
11. Replace this value with the URL copied from the Connected App in Salesforce
12. Click Save