Exception: use_certificate_chain_file: asio.ssl error

[timbo100]

I'm unsure what exactly this error message is saying when attempting to run the echo_server_tls example:

websocketpp/build$ bin/echo_server_tls 
on_tls_init called with hdl: 0x5a04750154a0
using TLS mode: Mozilla Intermediate
Exception: use_certificate_chain_file: asio.ssl error

I first assumed I was not generating keys and SS cert properly using the following command:

websocketpp/examples/echo_server_tls$ openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -sha256 -days 3650 -nodes -subj "/C=XX/ST=Alabama/L=HSV/O=Company/OU=Engineering/CN=localhost"

But no joy with below linds. Then I thought to make the filename invalid, and still got same error, so in the echo_server_tls example the lines:

        ctx->use_certificate_chain_file("~/workspace/Websocketlibs/websocketpp/examples/echo_server_tls/cert.pem");
        ctx->use_private_key_file("~/workspace/Websocketlibs/websocketpp/examples/echo_server_tls/key.pem", asio::ssl::context::pem);

Don't appear to be reached or executed properly. since renaming key.pem to keyx.pem and cert.pem to certx.pem did not change the error message.

1. please confirm that I'm generating self-signed cert and keys for testing properly
2. what does this error mean and how do I fix it??

Thx