I presume you have your sat cables plugged in? top left, bottom right? I am also presuming your screen, when pressing EPG, looks like the screen shots provided in the instructions? And lastly I presume you are using a Zgemma H2S box?
When the box gets flashed with the image and first boots up it actually has no choice but to display BBC1 HD or at worst a black screen.
Maybe it is worth starting from step one again?
I was replacing a Humax box in the kitchen, which had been pumping out freesat, using two LNBs, for years. Well, so I thought. Only one of the cables was working! I swapped them around and now everything is fine.
Moral of the story is:
Don't bother configuring anything until you can get a free to air channel working. If it's not working then check the cabling and or swap them around. Finally go to Menu->setup->Service searching->Signal finder. Use the left and right arrow keys around the OK button on the remote to move between tuners.
Thanks for the help.