ferdhelke,
I have taken a look at your nation Cornish Republic on LU. You're doing well, and your unemployment is quite low by Simcountry standards.
If you already have production plants in stock. Then my best guess is that the game is preventing the Corps from being built, to prevent worker shortages.
Simcountry nations require a little bit of unemployment to function well. Otherwise Corporations and Government facilities might have to close down. Once your workforce grows, the game might allow the Corporations to be built.
Beyond that, we'll have to wait for input from the GM's.
Signed President of DanNation on LU