Thanks for your help. I presume there is a setting on the Humax to switch off the standby mode when required.
I noticed Power Saving in Standby is currently set ON (I guess it is the default) and read the notes in the manual. I set this option to OFF, meaning "do not save power", but LAN access is still not possible. Standby is Standby, no matter whether saving power or not. I guess linux has stopped running in this state.