Hello!
I've tried to complete objective 7 where I should interrogate some diplomats and send my own diplomats to some countries. I've successfuly captured all the diplomats but when I tried to interrogate them they just died :). Really, I don't get any diplomat, just plastic bags :)
But new missions appear on the object screen (those where I should send diplomats back)

you need to send your own diplomats back.
not the ones you interogate as they have to die as far as I know.

Just solved the problem. I just kidnapped a diplomat from Russia. Earlier I didn't found any of those guys in the world so I tried to interrogate emenys' diplomates to get the own one

you are getting close to end now. Have fun with the rocket testing