Answer
Once SSL Proxy is configured, the older direct application-server URL stops working entirely by design — that's expected, not a sign of misconfiguration on its own. Instead, reach the Admin Console through the environment's proxied public-facing domain, appending either /admin or /index_admin.html to that public domain (e.g. https://<public-domain>/admin), which should present an 'Other Links' page from which the Admin Console is directly accessible. If neither of those specific paths works under SSL Proxy, that specifically indicates the IFS Applications SSL Proxy configuration itself hasn't been set up correctly, rather than SSL Proxy being fundamentally incompatible with Admin Console access.