Just out of curiosity, is the NAS IP on the controller configured with the IP of the controller on the Configuration>Authentication>Advance>RADIUS Client> NAS IPV4?
Also i noticed you said:"...Controller = 192.168.41.245 (MM)" , in Aruba OS 8.x users are Anchored in the Mobility Controllers not on the Mobility Masters. So in this case, you should send a disconnect message to the controller where the User is Anchored.
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Shpat | ACEP | ACMP | ACCP | ACDP
Just an Aruba enthusiast and contributor by cases
If you find my comment helpful, KUDOS are appreciated.
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Original Message:
Sent: Jun 10, 2025 05:51 PM
From: Adam Newson
Subject: RADIUS CoA ClearPass/ AOS8 controller issues
@shpat thanks for that. After select the MAC address delimiter to include the colon as suggested above, it doesn't appear to have made a difference. Still 'no response from network device'. Although, the MAC shown below does now appear to include the colon delimiter. Also attempted selecting the lower case option, but I don't think the controller would care about this? Any more thoughts?

Original Message:
Sent: May 23, 2025 11:55 AM
From: shpat
Subject: RADIUS CoA ClearPass/ AOS8 controller issues
Try to change the format of the MAC Address - Calling-Station-ID Settings under the AAA configuration in the controller.
I think that the controller does not understand the format without Colon, so when you send a COA, it will return the error you are seeing because that mac does not exist. It is expecting the message to be xx:xx:xx:xx:xx:xx

Maybe this post would be helpful.
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Shpat | ACEP | ACMP | ACCP | ACDP
Just an Aruba enthusiast and contributor by cases
If you find my comment helpful, KUDOS are appreciated.