or
HTTP 415 Error : Missing Content Type
Webpage says (check in Fiddler or LR) -
"RecContentType=text/html",
"EncType=application/json",
most probably earlier failing request had following -
"RecContentType=application/json",
and no EncType defined.
Error comes because of the body contains json content with some special characters which are used as delimiters in Load runner.
Also make sure "Enable Data Format Extension" is checked in Run-Time Settings -