Two quick things to check: salaries and shortage in a single worker catagory.
SALARIES:
Check the Salaries settings on your Corporations page. If your salaries are too low, people wont want to work at the corp. You'll need to adjust them to find a nice balance (because higher salaries obviously means the corp has higher expenses. But employees are better than no employees.)
Try setting them to 200-220 for all corps. (It may take a few gamemonths for the corps to get to that salary level, depending on where they are now. But you should begin to see the corps hiring more people.)
EMPLOYMENT:
On your Employment page, scroll down and just check you have enough "unemployed" workers in EACH catagory to satisfy the number of needed workers for 100% production and hiring.
If you notice a shortage in a single catagory, it will prevent other workers from being hired. (Ex. You cant hire a
J
Josef Lenin (White Giant)
All worlds
thanks, that helps a lot :D