It's been a long time since I've played but I think you may have other areas zoned for farming/industrial and those might be getting done first.
No, I've started two cities now and I couldn't get any farming to build on either. I had no other districts in place at the time. Could it be the type of land I'm trying to build farms on? When I look at the colour codes in the map, there's forestry, oil and ore, but no zone colour for farming.
Also, I bought another tile of land, but then realised there was hardly any land there. Is it possible to reverse the buying of land tiles? Can't figure out how.