Most likely your DVD recorder doesn't have a digital tuner as manufacturers are only recently adding them to the recorders.
So, instead you need to tell the DVD Recorder where to find the Digital Signal which it obtains from the TV. ie. The socket on the back of the DVD which connects to the TV. Usually, named AV1 or AV2 or Ext 1 or Ext 2 or similar. Look for a button on your DVD Recorders remote control to switch to the socket.
(If you are still unable to record, check for settings within the TV's menu to enable DVB, Analogue or Monitor output from it's rear socket and set it to DVB.)
PS. If you want to make a timed recording there will probably be a feature within the DVB Guide to set up timed programmes directly rather than having to bother with Video + or manual programming.
Cobweb, August 2005