I also encountered this error. However, I figured out the reason for my failure. I have the Dual tuner Tablo and I had tuned 2 Live TV channels at 9 AM last Thursday. 1 of the Live TV channels had a weak signal strength (aka get pixelations once in a minute). When I would try to tune another Live TV channel at say 9:30 AM I would get the error about No Tuner Available. Basically, the 2 tuners were ‘locked’ to the other 2 channels and would not be released to tune a 3rd channel. So I figured let’s see if a recording has higher priority and can re-tune one of the tuners. A recording was scheduled for 10 AM on a 3rd channel. However, the tuners remained locked to the 2 previous channels even when I stopped watching any TV at 9:30 AM. This resulted in show listed below not being recorded, but the reported error was the hard drive was full. I can assure you the HDD was not full and had enough free space to record a one hour show.
I was able to replicate the issue of not being able to tune a 3rd Live TV channel after tuning into 2 Live TV channels as long as 1 of the Live TV channels had a weak signal. So maybe @philsoft this is what happened to you? Were you recording anything shortly before your show was scheduled to record? Or possibly watch Live TV shortly before?
You have my Tablo MAC address, please let me know if you grab the logs off of my Tablo. I will delete the failed recording after.