Hi Gordon, we had that as well...
For a Grundig
Go into the Menu using the menu button on your remote
Then settings
Then First time install
Install
Enter lock code 0000 zero, zero, zero, zero
Then press OK, and again when the screen prompts
It will then scan and should restart automatically, if it doesn't switch off at the mains, leave for 10 seconds and switch back on again.
You should then have all of the channels back again..
If it isn't a Grundig, refer to your manual to do a first time install. (Most manuals are online)
Paul..