Started a new game and noticed that " (12) Construction IV" technology cannot be completed because (14) GRAPHITE is needed to make molten silicon that is locked; to make Electronics II. So, making it impossible to progress unless you find traders for graphite or silicon.
Look at the Technology tree and look at "(12) Silicon & Electronics" requires graphite to make molten silicon; graphite is a (14) Chemical Plant II skill that makes it.
(12) Construction IV unlock requirements require you to make Electronics II chips which requires silicon and that requires graphite.
