Today, I am getting the message Retrieving quality profiles, try again in a few minutes when I trying to add a new TV show.

Not sure if this is something that has been introduced in the latest develop version of NzbDrone (v2.0.0.1717 ), or it it's a bug.

Image Image Thanks.
I'm not sure if Kev supports the development branches. You could see if the problem also occurs with the stable version. Or the previous working version you used. If it does then see the changelog for anything that might have caused it.
I was thinking that as well, but thought it would also give Kev an heads-up about an upcoming issue.

I'll revert NzbDrone back to master tomorrow and try again.
I just added Izombie using nzb360 connected to nzbdrone 1690 master, worked well. Seems to be the first episode is today? Might as well watch now that I've added it :P
Is there anything in the logs ? Check nzb360 logs (catlog), nzbdrone's logs and if you know how, capture the traffic between the two and see if there is anything wrong.