When attempting to add or register a token credential, an error occurs:

VIP Error: Failed to register Symantec Credential. Credential is not valid

The token credential is not associated with the client.

From the VIP account manager, search for the Token \ Credential ID. Or, search the credential ID at https://vip.symantec.com. 

If it is a valid credential but cannot be found in the VIP Manager and an error occurs, contact technical support to do a system search and determine the state of that credential.