Hello,
Did you change just the certificate or the hostname too of the controller?
I would check few things below first:
1. Is the client able to resolve the hostname of the controller? Nslookup etc.
2. When you enter the credentails and click on login on the client, what is the url that it trying to post the credentials to?
3. pcap from the client machine, would show, if the client is able to post the credentials or not, and failing?
4. If the client is not able to post the credentails and failing, we need to look at the acl's.
you mentioned it was working before and stopped working after you updating the certificate? did the CN name changed on the certificate? if yes, we need to update the CN name on the Clearpass Guest configuration, under NAS vendor settings.
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