Still a problem with using commodities?
Know the above thread is quite old but are people still having issues using the commodities to upgrade? Finding it only in single player - seems to work fine in multiplayer games. SO annoying!
It's a known issue, but the work-around is to click on the actual progress plaque at the lower right where your pieces are. You will probably have to zoom out or scroll down to it, but clicking on the color portion of the plaque corresponding to the improvements you want to make will let you make the upgrade when clicking on the city won't.