Trouble setting up HTTPS

Hi, I am currently trying to set up SSL with a certificate signed by an internal CA so we can secure the connection between the reverse proxy and Keycloak 12.
When trying to test the connection I only get the message that there is no cypher overlap. I am not really sure how I can fix this.
This is our standalone.xml standalone.xml · GitHub (Some elements have been removed for privacy reasons)
The used keystore is of the JKS type and contains a PrivateKeyEntry with the alias set to the hostname of the certificate and a trustedCertEntry named bundle which contains the ca-bundle required for the certificate.
When trying to connect using openssl s_client it fails the ssl handshake with alert 40.

So can someone help me with how to fix this issue?