What happens when you try to play back an analog hi-8 tape? Is the video clear? You need to test this. My guess is that the heads are clogged or something else in the video path has failed and the camcorder no longer recognizes digital-8 data as it's not getting it or it has too many errors to play. The tape counter data is written while you're recording video so if you have no video/no data you'll have no tape counter. A blank tape will exhibit the same behavior.