Remove non trusted certificates

Okay, the error you’re reporting here is likely a subscribed calendar, the target domain for the subscribed calendar appears misconfigured, and this stuff is ~unrelated to the trust store, and the zz app stuff is another domain associated with the same domain that you’re having issues with. (There are a gazillion top-level domains like the familiar com, net, and org around, and app is one of the many others.)

Hi Viddavisda,

Thanks for using Apple Support Communities. Are you using a manage device from a school or from your job? If so, you can see how to remove any configuration profiles here: Install or remove configuration profiles on iPhone - Apple Support

"You can see the profiles you have installed in Settings  > General > VPN & Device Management. If you delete a profile, all of the settings, apps, and data associated with the profile are also deleted."

Please also take a look at the following: Trust manually installed certificate profiles in iOS and iPadOS - Apple Support (IN)

Cheers.

That's likely a subscribed calendar.

Check for and remove any calendar subscriptions you don't recognize from the list of subscribed calendars.

To check: open Calendar app, select the Calendars button at the bottom center, and look for a block of Subscribed Calendars.

Details: Delete spam calendars and events on iPhone - Apple Support

Hey there Viddavisda,

As you mentioned you restored your iPhone from an iCloud backup, this would make your iPhone as it was when you made the backup. We also don't recommend restoring from a backup as a valid troubleshooting step for the question you're asking.

Moving forward with troubleshooting, we wanted to confirm a few things based on the details you shared so far, along with the links shared earlier:

1. Do you have any provides currently installed if you check under Settings  > General > VPN & Device Management?
2. Where exactly are you seeing the message regarding 'dnsdun non trusted certificate', and when did it start to show?
3. Did you purchase your iPhone used, or brand new from an authorized Apple reseller?
4. What do you see under Settings > General > About > Certificate Trust Settings?

Have a good one!

Viddavisda wrote:

Thank you for your suggestion.

I’d like to try disabling the calendars first to see if it will solve the issue. Do you think it would work as a temporary fix? That way I can zero in on which calendar is causing the problem.

Do you have a subscribed calendar? A subscribed calendar, specifically. Not one of the other types of calendars. It'll show in a block labeled as a subscribed calendar. Most folks don't have these. There's a picture of a subscribed calendar block here. If you do not, then I'd rather not waste everybody's time here. If you do have a subscribed calendar, then I can probably explain a little more.

Viddavisda wrote:

Yes I have a few subscribed calendars such as US Holidays, Earth Seasons and a calendar from my place of work. I have disabled them and am waiting to see if the issue resolves. Someone else in this thread has weighed in that zz.app has not upgraded its compatibility with current versions of iOS. Do you know if these components are at the root of some of these subscribed calendars. Thank you for your time and input.

As I was apparently unclear, I suspect the fundamental issue is a subscribed calendar.

Does the information available for any of the subscribed calendars match the domains shown?

zz.app has not updated their credentials to work with iOS 15.7 and/or iOS 16. When they do, the message will not appear.