When trying to register a new DLP Cloud Detection Server as an External Appliance in the CASB server, the error appears despite having a non-expired, unique token for the purpose.
"DLP should be enabled when activating DLP appliance."
It's hard to notice sometimes, but there is a button to "enable" the appliance, prior to registration and activation.
Use the option to Enable the appliance, then use the drop-down menu under "Actions" to Connect and Activate the appliance.
There are a few token-specific errors which indicate an expired token, use of an incorrect token, or an incomplete profile on the DLP Cloud Detector (which also prevents registration in CASB for a new DLP Detector).
Here is a landing page for other errors which can occur when attempting to register a DLP Detector with CASB: