Not sure about the logic of this but it often works for me when one or more freeviews is missing. I use the guide button to record something soon - anything - and just okay it. Often, usually when you don't want it, you get a message which offers to update all your channels. Only takes 3 mins but you lose anything you've pre-recorded.
Hopefully, that update will restore missing channels. I'm sure there is a way of summoning this channel update deliberately or doing a trouble-shoot properly but I can't be bothered looking up the manual unless I'm totally snookered.