Sharepoint: OpenSearch common forms/cookie authentication -

i have opensearch provider trying integrate sharepoint (online). provider protected authentication.

sharepoint supports cookie or form authentication opensearch. when give url login page , click enter credentials shows page, enter credentials , shows popup asking if authentication successful. clicked yes , gives following error:

"an error occurred when communicating remote server. may because url provided malformed or site might unavailable or not reached within specified timeout or proxy settings not configured."

i have tried multiple sites, including example google: https://accounts.google.com/servicelogin?hl=fr&continue=https://www.google.fr/%3fgfe_rd%3dcr%26ei%3d9j-lvdxlmyxf8aesrk-4dg%26gws_rd%3dssl#identifier

do know if there required configuration on site?