I’m not an expert but perhaps the signal from the aerial is not strong enough to pick up any stations? I have to say that after several months of trying, with new set-ups and different hardware I’m still experiencing poor performance from a Raspi 2 set up with tvheadend. Typical issues I am experiencing on a regular basis are
Timeshifting doesn’t work
Video and audio trying to keep up with each other makes the output sound like an old stretched tape (if you are old enough to remember this sound)!
Timer issues (won’t allow me to set a timer to record a program)
I have spent several days trying to track down the issues with no luck, so when you get around this issue you may be faced with many more! Good luck anyway!