Why cannot a device added under central device management be removed completely?
The device-list on Central's device management page, is merely a reflection of ownership of hardware, & is not list of managed devices by Central. It shows a list of hardware you own as a customer, per supply chain records. So you cant really delete an AP from Central. You can however un-assign license to it from Central. This will cause the device entry to be highlighted in red. At this point, anyone else who takes that device under management, by adding the device under a different Central account, will make it disappear from your account. If you are trying to add a device and it says in Central, it is "blocked" that means, some one has added and assigned a license to this device