1) The host and port are enabled in proxy and can be verified via curl -v -x <proxy name>:<proxy port> <End point URL>.
2) We are on 7.21.
3) No JVM arguments are added (https.proxyHost and https.proxyPort). We are creating the proxy page dynamically and passing it to ServicesUtilities • pxApplyHTTPProxyConfiguration--(Object,boolean,ClipboardPage)
aProxyConfPage is a ClipboardPage of class 'Data-ProxyAuthentication', containing proxy configuration details. If it is null, details will be sourced from standard proxy JVM arguments.
Have you tried the setting the below class properties on aProxyConfPage clipboard page, before you pass it to apply HTTP proxy configurations as pxApplyHTTPProxyConfiguration(client, isSSL, aProxyConfPage).