16024: Invalid participant label, must not exceed 128 characters, must not be a CallSid

The participant label specified in an API call to create a voice conference participant exceeded 128 characters or was in the form of a call SID.

A POST to conference participants call to the Twilio API specified a participant label which is greater than 128 characters or which resembles a CallSid ("CA" followed by 32 lowercase hexadecimal characters).

Shorten the length of the ParticipantLabel parameter or avoid using a CallSid.