Undefined index: HTTP_X_ELGG_APIKEY

runtime_errors":["DEBUG: 2019-11-07 13:16:34 (PST): \"Undefined index: HTTP_X_ELGG_APIKEY\" in file \/opt\/bitnami\/apache2\/htdocs\/engine\/lib\/web_services.php (line 558)"]}


Add the  following header in the request

X-Elgg-apikey

with api key value of elgg site

ref: 
http://learn.elgg.org/en/2.0/guides/web-services/hmac.html