If you followed security best practice and disabled TLS 1.0 and 1.1 support, you will get such issue. Although most of browsers will (or already) depreciate the support of TLS 1.0 and 1.1 in their newest browser and most of websites have enabled TLS 1.2 support and use the highest standard as preferred choice, some back-end support systems may still use old standard as default. Use the registry to modify .NETframework parameters to force it to use the highest standard for encryption. See EAGCTX's post for details.
