To change the IdP initiated SSO redirect URL use the steps below:
  1. As an admin Sign in to: https://signin.blackbaud.com/userprofile/
  2. Click Manage Single Sign-on button
  3. Go to Redirect Settings at the bottom right and click Edit
  4. Enter https://renxt.blackbaud.com to redirect to Raiser's Edge NXT
  5. Click Save, and sign out
  6. Go to your OneLogin dashboard and it should redirect to Raiser's Edge NXT

For more information review our documentation for OneLogin