Its happening here too, with a 4-tuner Tablo and one of my strongest local stations (and attic mounted antenna, catching a signal from 6 miles away.)
On the PC, running the web app,I go into "Recordings" and pick the "Most Recent" tab. It shows a recording for "ABC21 Local News at 6", which is a "Keep 1" daily recording. There are no episodes listed as available to play. Click on it; nothing happens. The event did air last night as scheduled.
Jump to the Roku, using the "Most Recent" Recordings feature. Here, instead of listing the item, the display shows a blank spot where the info would go, between "NBC Nightly News" (which follows immediately after, at 6:30 pm) and "Castle" which recorded earlier in the day.
At 6pm, only the ABC21 News is sched to record; at 6:30pm, I have 3 tuners used to record. ( I was not watching any Tablo recorded programs at 6:30, that could have interfered with the earlier program from completing, and no conflicts were recorded.) The 6:30pm network news recording on ABC21 was captured just fine. It appears that this is not because of tuner unavailability. I am not sure if one of the kids had the 4th tuner set to a channel when they came to dinner. Don't recordings take priority over "watching"?
I will delete the ABC network news at 6:30pm to see if this "clears" the problem, and report back. This is the only time of day that I have 3 tuners all actively recording at the same time.