I hit this on a new cluster on 10.5 - the Idle URL enterprise param wasn't set. I enabled auto-reg, phone registered but kept trying to query https://ucmpub/cucm-uds/xps/selfProvision, which came up with an error.
Setting the service param did not resolve the issue. I noticed that this was getting hard-coded into the phone's config. I traced this back to the Universal Device Template's configuration. It's another step to change when setting up a new cluster I guess?
In User Management -> User/Phone Add -> Universal Device Template there is an "Auto-registration Template" created automatically with a certain Idle URL. This template is used by default when auto-registering. So change this, or change the Universal Device Template used when auto-registering.
I got the same issue when I changed the hostname of my server.
However I haven't already found a good URL to provide for having an Idle screen
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The short answer is that you don't.... That isn't entirely true while at
the same time it kind of is, but for the most part you don't configure
the softkeys. You enable or disable them via TCL. Here is the long
answer. Be sure to read the whole thing or e...
Topology: IP Phone > Switches > Microsoft NPS setup to forward 802.1x
proxy to > ISE 2.1 patch 3 Authentication: EAP-TLS using Cisco MIC SANs
Phone Models 802.1X support? 802.1x flavor Addtl Comment EAP-MD5 EAP-TLS
Cisco 3905 Y Y N Cisco 6911 Y Y N Cisco ...