First off, every setting on my Android phone is correct – all location services, yadda yadda.
I would have my transit card appearing in Google now virtually all day, till bus service ended. I live 2 doors away from a bus stop.
I had this working perfectly for months, I have my home and work location in Google maps.
What has changed is that I was only working temporarily, until a couple weeks ago. The card stopped appearing 2-3 days ago.
As a stop gap measure I am using the traffic card with Transit selected. But that’s really Navigation. I know Google Now watches your behavior. Yes I’m not going to that area as frequently as I was, but I still need the transit cards for my day to day life.