This is a note to me in the future and anyone else with the same problem: My DirecTV TiVo stopped recording programs last week. After troubleshooting with a couple of friends with greater TiVo knowledge, I tried rearranging items in the Season Pass list, which typically takes several minutes for the TiVo to look over two weeks of programming and do its priority sort. (It must be processing millions of combinations -- some kind of truncated traveling salesman approximation?)
Once having done that, the TiVo To Do List showed upcoming programs as being on the list to record. Some bit broke!