GeoMedia SmartClient 2018 is unable to display layers of specific HTTPS-based WMS Service which has DTD document reffered through HTTP. The error usually tells following:
External DTD: Failed to read external DTD 'WMS_MS_Capabilities.dtd', because 'http' access is not allowed due to restriction set by the accessExternalDTD property.
Recent JDK versions by default do not allow HTTP links in HTTPS-based XML document (e.g. OGC service capabilities). To change this behavior, you must define javax.xml.accessExternalDTD=all for the JVM used by Hexagon App Launcher.
The support way of doing this is creating a new environment variable: