I\'ve placed my keycloak server behind apache proxy:
ProxyRequests On
ProxyVia On
ProxyPreserveHost On
SSLProxyEngine On
SSLProxyCheckPeerCN on
SSLProxyCheck
Your proxy should add forwarding headers on the proxy such as X-Forwarded-For, X-Forwarded-Proto and X-Forwarded-Host, this will allow keycloak to retrieve the client's (not the reverse proxy's) original IP which is important for security reasons. Also Keycloak can retrieve it's host name as it appears outside the proxy which should help with the Invalid token issuer problem.
Also you should configure Keycloak such that is uses the proxy headers, if you're using the Docker image do this with the environment variable PROXY_ADDRESS_FORWARDING=true.
Have a look at the documentation [1], you'll find more answeres there. [1] https://www.keycloak.org/docs/4.8/server_installation/#_setting-up-a-load-balancer-or-proxy