iCloud for windows not authenticating

Over the last few weeks iCloud for Windows has been increasingly patchy. I have traced this down to losing authentication and not authenticating when signing out and signing back in again. I enter the username and password, get the code pop-up on my phone, enter the code, then a wait until it times out stating there was an error in authentication.

My iPhone and Air are on the same network and are happily able to authenticate and share files across photos, I can access iCloud.com from my PC. I have uninstalled, reinstalled, rebooted, the works, and eventually it will authenticate work happily for a couple or days, and then break again (no reboots etc. in between). It's driving me nutty, and ideas!