are you sure it's the pirate strong hold you can't build?

please look into the construction tab to your right, 

all buildings are in there that you can build 

also make sure you have the correct amount of resources, prolly why its not hightlighted is because you might be low in those resources,

and or have something else building 

Thanks for Your reply,

I do have enough resources and in the Menu it is higlighted. When i try to build it there is no place that Highlights (like with all the other buildings) wherever i try to place it.  i tried numerous times but it just does not work.