Factory facility upgrade

What are the requirements for a facility upgrade? 
Do you need to be on a certain level? Im at williams in S3 now, at facility spec 2 since mid season 2. Can't buy updates because ALL next updates require facility spec 3.
I have resource points on increased for me. So yes I have all updates. But now in game I havent got an update for over a year.
I cant find what the requirments are for the upgrade? Does anyone know?

FYI, I'm playing co-op career. Not my team. 
thnx!