Azure web app service to call onpremise WEB API using HttpClient using hybrid connection manager

We have onpremise web service (asp.net core mvc) deployed on local network machine. We are trying to call these WEB API using App Service deployed on Azure. But it is giving time out error or Task was cancelled error in case when we try to connect it using “HTTP” Protocol. In case of “HTTPS” it is giving “security error occurred error“.