I think he's saying the CS he is allied with has coal resource plots with mines on them; but no coal is going into his resource bar.
Oh, of course. I misunderstood.
Can the OP upload a save or screenshot maybe?
My allies have 14 coal hooked up, but I'm not getting any. I have steam power, but is there another tech you need to be able to use coal? I don't have metallurgy. There are no wars or blockades.
The CS must have Steam power too.
Interesting. Never really occurred to me that CS are also researching techs. How is the advancement along the tech tree organized? Do they really research specific techs or do they get a tech automatically when everybody else has it?
City states have their own tech tree. It's short enough for the city states to follow the research of an average civilization. If you get really big and out-tech all your opponents, you will probably out-tech the city states too. But then again, you probably won't need their coal, oil or uranium when you are that big.