I'm pretty sure this is not a problem with Transmission, but with either something else on my computer or with my DSL ISP. The problem is that, except for a couple of successful downloads and partial downloads with the two programs about a week ago, I haven't been able to either download or seed anything at all with either Transmission or uTorrent.
When I use the Tracker tab of Transmission's Torrent Inspector, I always see the messages:
Announce failed: tracker did not respond.
Scrape failed: tracker did not respond.
This happens consistently with numerous trackers and numerous torrents. It's probably why there are always 0 peers for a torrent, even when I know that a particular torrent has many seeders.
BTW, I'm running OS 10.5.8 on a non-Intel Mac. I don't have a router connected, and the modem is operating in bridge mode, AFAIK. Is there some setting I'm not thinking of that I might have to change?