This was a head-scratcher for me, and I'm curious if anyone else who uses window antennas has experienced the same thing. We recently had new windows installed in our home, which ended up negatively affecting the Tablo reception afterwards. I tried putting the antenna exactly where I had it previously, but all I literally got on the device were the native streaming channels offered; not one local station was available. I moved from window to window in the home, all with the same empty result.
In researching a bit, I learned that new windows contain a level of thin metallic coating (for heat reflection and insulation purposes). This is what was preventing any reception. Out of desperation, I placed the antenna on the wall next to the window as shown. I had very little confidence that this would work, but (nearly) all the local stations came in at full strength immediately on the next channel scan. To paraphrase the Stones: I didn't get all of the channels I wanted, but I am getting all the ones I actually need. The wife isn't thrilled naturally, but she's working on some kind of treatment to cover it up. Needs must.
We are 30 miles from the towers and I'm using a 4th generation model.