Without knowing how the track was created, I can't guess how the durations got set to zero.
How did you determine the durations were zero?
The edit menu has a "length...." command but it only increases the length by some percent and 200% of zero is still zero. Doesn't help your case.
There is the edit menu command called "Interpolate...". It is quite mysterious but it will do the trick for you.
1. Select all events in the track.
2. Click Edit Interpolate..... This brings up the Event Filter - Search dialog box. Make sure everything is selected by clicking (in lower right corner) the NONE and then the ALL box.
3. Click OK. This changes the dialog box to Event Filter - Replace.
4. In the first row (for Notes), change the minimum duration to something like 200. Then click OK. All the notes in the drum track should be at least 200 now.
As far as I can see the Replace operation doesn't actually replace. It seems to do something like add the minimum length to the existing length. So if there are non-zero lengths, the end result is something larger than 200.
Note that in the drum track view, all the drum notes are shown as very short "hits". They will not look longer as you make their durations longer. If you want to really see the note lengths, just temporarily change the channel number (in the track view) to something other than 10.
Good luck on this!
--Larry