If a Marketplace app activation key is acquired via OrderId, the Liferay bundle will try to validate the key by accessing www.liferay.com.
This is an issue if the server requires a forward proxy to access the Internet. The Java proxy properties that would be put in JAVA_OPTS or system-ext.properties are not currently functional.
Resolution
What's needed in this case are activation key proxy properties with values that correspond to the server in question:
license.proxy.passwordlicense.proxy.portlicense.proxy.urllicense.proxy.username
The properties are available for use in the portal-ext.properties file. They make it possible to activate a Marketplace app on a Liferay server that is behind a forward proxy.
Additional Information
A workaround to this is to use a activation key .xml file, which does not validate against liferay.com.