So, basically, I have the problem as described in the title. My city was growing well, I got to 200k population, I have all five ultimate buildings. When suddenly I notice that both my industrial and commercial zones are having problems. Industry complains that nobody buys the products, commerce says there's not enough of them. This only affects the regular industry; forestry and agriculture seem fine. The problem appeared out of the blue and it's been happening for over two in-game years already. Both industry and commercial buildings are getting abandoned and do not rebuild, I've lost about a quarter of each already. A quick look at the outside connections shows that the share of "goods" in both export and imports is almost invisible. Traffic is not a problem, and I even have cargo train terminals in both areas. Any ideas why this might be happening and how to remedy the problem? I don't want to abandon my city, I've already laid out huge road networks over the entire map, and I really want to fill them now =)