Looks like you are expecting SSO to work but users are getting prompted for credentials. Let's do a quick check of the browser settings to ensure you can leverage SSO from browsers. Log into the client machine where the issue is happening.
Internet Options settings
Open Internet Options in the control panel
- Under Advanced, check the state of Enable Integrated Windows Authentication. Ensure that the option is enabled or checked.
- Go to the Security tab
- Go to Local Intranet > Sites > Advanced, check that the AD FS URL is listed. For example, if your AD FS service FQDN is fs.contoso.com, you must see an entry for fs.contoso.com in the list of websites.
- Click 'Custom Level' button, under User Authentication section, find 'Automatic logon only in Intranet Zone'. Ensure that it is selected.
Usually group policy is utilized to ensure these settings are set as required on all the domain joined machines.