Often the cause for CoA issues
- Rfc3576 not enabled on the WLC. Newer IOS version come default with the new RFC5176 which Aruba doesnt support. You can still force the Cisco wlc to use rfc3576 tho.
- Udp 3799 FROM Clearpass to WLC is not allowed in firewall/access lists. Often it's opened the wrong way.
- Wlc is configured with the wrong Radius Client IP. Verify this on the access tracker - Input. Check that nas-ip-address is the same as connection:nad-ip-address found under Computed Attributes.