From Tim at Tablo support: “Can you try running another channel scan but this time, make sure you hit the "Add to Guide" button on your screen when the Tablo channel scan finishes? This will ensure the frequency change is saved to the Tablo database, which in turn ensures the Tablo isn't trying to access the old, empty frequency.”
This worked for me after I removed my distribution amp to stabilize my signal.
I have a Cm-7777 preamp with a 4 port distrubution amp. I removed the distribution amp before Tim’s suggestion worked, but the “Add to Guide” after the rescan seemed to work for me. I had tried the adding the rescanned channels to the guide previously with out results but tring it again after removing the preamp, I did the “Add to Guide” and having been receiving WFAA ever since then.
I also had to reorient my antenna. Since I have a multi path situation that was tricky.