Private Web Certificate issue with iOS 18

We currently are using private web security certificates for our URLs. Our users download, install, and enable a Root Certificate on their devices to reach our website (trusted). The web security certificates have expirations that are less than 13 months from expiration.

Since the deployment of iOS 18, our users are now getting a "This Connection is not Private" warning in the web browser on both Mac and iOS devices.

What change was implemented in iOS 18 that is causing this issue? Other than changing our web security certificates to Public ones, what solutions should be implemented to prevent this from occurring?

Private Web Certificate issue with iOS 18
 
 
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