I am trying to add the "Sign In with Apple" to my existing App ID. After checking the option to enable it, the following popup was shown: with this message:<blockquote>
If you're enabling an App ID for the first time or for a new app, enable the App ID as a primary. You can use primary App IDs on their own or to enable identifiers for related apps and websites through grouping. To enable an App ID for a related app, (for example, an App ID for the iOS version of your Mac app), group it with the existing primary. This will also ensure that users only need to provide consent to share their information with you once for each group of apps and websites.</blockquote>
However, I could not proceed because the Save button is disabled. I could not do anything.
are there any extra configs I missed or are there anyways around to enable an App Id as primary?
First You have to go to Xcode > Signing & Capabilities > + Capability and Add Sign in with apple as a new capability.
After that refresh the developer.apple.com page and you should be able to select Enable as a primary App ID and the save button should be enabled.
The UI is confusing, what I did was selecting sign in with apple first then immediately clicking save/continue. Don't click configure yet, save first. Then Click cnfigure and enable primary ID.