When creating a new airport there is no possibility to sign a contract with the builders. Choose not signed contracts and there simply a white screen
Try F10, regenerate contracts.
I 've started a new airport since new update, no problem for me. Not sure why you called it ‘not signed’, I’m pretty sure the name is ‘Offered contracts’
This is a bug that happens when you load a new game, or start a new game when you’ve already played a session. It will get hotfixed on Monday but if you restart the game the contacts should generate correctly (unless you again boot a new game from an already started session).