Keep an eye on your local and regional traffic - especially with resources, which are purchased and sold by truck through the region. If you have major traffic jams, part of the game is solving those issues. Max out your delivery trucks, place trade depots near the entrance to the city with a straight shot out, settings correct, etc.
There is a bug that will sometimes cause the trade depot trucks to stop for some reason. Watch to see if trucks are coming or going; if you have an issue, go into edit mode and delete and rebuild the garages. It's not necessary to demolish the whole building, just the truck garages.
Also can sometimes be helpful to just exit the game and re-enter. This will reset the traffic and you can sometimes get things to move just by doing that. Happy building!