iPad Pro 9.7 won't update

We have an iPad Pro 9.7 that says it is up to date on iOS 10.0.1 - why can't we update it to iOS 10.3.3?

There is a red "badge" 1 in settings showing that there should be an update available - but when we click on it - it says "iOS 10.0.1 - Your software is up to date".