Have you solved 479 or more? If the answer is yes then sorry you have solved all Inno will allow in terms of expansions. The remainder are tech tree or premium expansions
I had solved 459 I think, didn't realise it was capped. seems a bit of a swizz. Tech expansions are few and far between. Seems I've come to the end of the road as far as expansions are concerned. Seems a little unfair you are able to expand more with cash than you can with hard work.