I emailed Chris at humax and he sent me this when I had the same problem.
Please follow these steps to refresh the tuners and manually tune into your local transmitter (Winter Hill):
Power OFF the receiver
Disconnect the Aerial cable
Power On the receiver
Press MENU
Select Installation
Enter your password (default = 0000)
Select Default Setting
Select YES
Enter your password (Default = 0000)
When the receiver restarts, power off
Power on the Box
press ok on stop (when you see automatic search)
'no channels found' press ok
'press ok to search channels' press ok
select manual search
carefully connect the aerial cable (whilst the box is on )
Then please follow the steps below.
The following procedure will allow you to receive signal from the Winter Hill transmitter.
Please go down to Network Search and select enable.
Then go to Channel and select 62.
Then select Search. When the search has finished, press save.
With Network Search enabled this should find all the channels on all multiplexes.
However if this does not find all channels you will have to search the multiplexes individually.
To do this please switch Network Search back to Disable and search the following channels one after the other, selecting save after each search;
62, 59, 58, 61, 55, 54.
Hope thisa is helpful,, it also helps with the problem of no epg working.