The title says 802.1X, your message describes captive portal login. What are you trying to do?
The Prevent CNA will prevent the automatic popup, which is needed if you want to use ClearPass Onboard to get your clients provisioned for 802.1X. With that option ticket you should not see the automatic popup, which looks to be the opposite of what you want.
For all devices to properly pop up for the captive portal, make sure you are using HTTPS based on a fqdn (not on IP), with public trusted certificates for all steps in the process (like controller/IAP and ClearPass will need to have a trusted certificate). If you see any certificate warnings or HTTP anywhere in the process, it's unlikely that the Apple devices will show the automatic popup.
If you want SSO against Azure AD to work (as the use has already authenticated for other applications), you should do that outside the CNA, in the same (Safari, Chrome, etc) browser that the user is logged into. If you combine 802.1X and Captive portal, I have seen some devices not triggering the popup when on an 802.1X network (just on open/PSK); so that may be happening here as well.
Is your question answered? If not, it may be good if you provide some more context and what you are doing.
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Herman Robers
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If you have urgent issues, always contact your Aruba partner, distributor, or Aruba TAC Support. Check
https://www.arubanetworks.com/support-services/contact-support/ for how to contact Aruba TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
In case your problem is solved, please invest the time to post a follow-up with the information on how you solved it. Others can benefit from that.
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