It was because IIS on Windows Server 2008 R2 build in Transport Layer Security in version 1 (TLS 1.0). That version is outdated and should not be used for securing any HTTPS traffic and also most of the browser didn’t support it anymore at the beginning of 2020.
What you need to do?
Install the patch for TLS1.2
If your server is up-to-date with all security patches offered by Microsoft, then you probably already have TLS 1.2 installed. and what you need to do if just enable it.
Else, you need to manually download KB4019276 from the Microsoft Update Catalog.
To enable to TLS1.2, You need to modify the registry to activate TLS 1.2.
You can click here to download the zip file to enable the TLS1.2 with double click inside the register file