Just adding my two cents to this discussion - I'm having the same issue, which is that since upgrading to Yosemite the automatic downloading of my subscribed shows has stopped. If I click the download arrow on the specific show, it works just fine. I'm using Vuze...
Likewise, I am also experiencing issues with Yosemite.
When I edit a subscription the new episodes are not show, but when I select 'edit' the new episodes do actually show in the feed. I have also checked the .rss feed that TVShows is using and have manually searched on various torrent sites, all of which confirm that new episodes are in fact available.
One show has managed to download itself, although it was in a rar format so I cancelled that and did it manually. I have told TVshows not to use rar formats so I consider that to be a bug.
Also, another show that was available in the early hours of this morning is not downloading. It is visible on the feed and the episode list for my show, but it simply hasn't downloaded and even the manual download button doesn't do anything.
Mine is functioning as normal now. There is still a long delay between the torrent being available (in 720p) and TVS actually grabbing it, but given that my entire download process is now automated (TVS > transmission > plex) I'm not complaining.