@Deep_Azure9 , Just checking in to see if you had got a chance to see the previous response by ricardosolisvillegas-4678. To benefit the community find the right answers, please do mark the post which was helpful by clicking on ‘Accept Answer’ & ‘Up-Vote’.

Just sharing additional info:

When an App hosted on Azure App Service, tries to connect to a remote endpoint over SSL, it is important that the certificate on remote endpoint service is issued by a Trusted Root CA. If the certificate on the remote service is a self-signed certificate or a private CA certificate, then it will not be trusted by the instance hosting your App and the SSL handshake will fail with this error.

If you want to have a private certificate, the certificate must meet the following requirements :

• Exported as a password-protected PFX file, encrypted using triple DES.
• Contains private key at least 2048 bits long
• Contains all intermediate certificates and the root certificate in the certificate chain

Just to highlight, App Service has a list of Trusted Root Certificates which you cannot modify in the multi-tenant variant version of App Service, but you can load your own CA certificate in the Trusted Root Store in an App Service Environment (ASE), which is a single-tenant environment in App Service. (The Free, Basic, Standard, and Premium App Service Plans are all multi-tenant, and the Isolated Plans are single tenant.)

We can also use curl -v https://www.bing.com to view SSL handshake via Kudu Console (https://<yoursitename>.scm.azurewebsites.net/ )

If you wish you may leverage free App Service managed certificate (ASMC), you may checkout the prerequisites and features and their limitations. The easiest way to add a private certificate is to create a free App Service managed certificate .