For what it’s worth, I just managed to solve a similar problem of vanishing native timecode (not sure if that’s the correct term, what I mean is the timecode stored on the tape, time the the footage was originally fimed, not anything added later in Vegas)
Native timecode, if we’re calling it that, is stored in many different formats (there’s not much standardization) and Vegas likes some and not others. In my case I had one long AVI that I used an outside program to split into scenes by timecode/datestamp (Ideally you do that during capture but this was after the fact). It would then output several AVIs with the timecode of each intact.
I had to go through a few different programs. The first three outputted AVIs which, when I checked using those programs, showed the timecode was fine (as did the camera). Vegas, however, didn’t recognize them, I got the zero issue mentioned above, even using the add timecode script, timecode fx in the media viewer, etc. no go same issue above.
I then tried a third program, and for whatever reason it exported the timecode-split scenes in a format Vegas 8 liked, problem solved (by the way it was scenalyzer live, the newer version not the old freeware)
So in these timecode zero cases, best to keep in mind the a) the timecode must be there on the original file/media, and b) it must be in a format Vegas likes. If not, you’re banging your head against the wall for hours like I just did thinking there’s a magic setting, when you need to go back to the AVI. (Maybe Vegas 9 is more accompanying, haven’t tried)
Like I said, for what it’s worth