Adding the return URL to the Apple Developers site

Copy the callback URL and paste it in the Apple Developers site.

Steps

In PingOne, go to Integrations → External IdPs.
Locate the appropriate IdP and then click the details icon to expand the IdP.
Click the Connection tab.
Copy the callback URL and paste it in a secure location.
On the Apple Developer site, click Certificates, Identifiers & Profiles.
Select Sign in with Apple and click Configure.
Select the primary App ID and click the icon.
For Return URLs, paste the value for Callback URL that you copied earlier.
Click Next, and then click Done.

Enable the external IdP. See Enabling or disabling an identity provider.
Add the IdP to your authentication policy. See Editing an authentication policy.
Add the authentication policy to your application. See Applications.