Trouble with Off air tuner.

I have an off air tuner.  When I set it up it shows all the channels with excellent to perfect signal strength in the signal meter but then when I go to watch those channels it says "searching for signal" and never goes to the channel.  Am I doing something wrong?  Why does it show perfect signal strength in the meter but no signal when I try to watch the channels.  All the off air channels work perfect when hooked directly to the TV and not through the tuner.