You attempted to initiate an outbound phone call or message, but the 'From' parameter you supplied was not a valid phone number or alphanumeric sender ID.
Twilio accepts phone numbers in E.164 format (i.e. "+1 format"), 10-digit US and Canadian numbers with any combination of non-digit separators, or Alphanumeric Sender IDs (SMS only) with up to 11 alphanumeric characters [a-zA-Z0-9]. Refer to this page for acceptable characters.
The number must not be on a do-not-originate (DNO) list, and Alpha Sender IDs may not be generic.
From
phone number is on a do-not-originate (DNO) list
From
number is assigned and not on a do-not-originate (DNO) list.