'Userpoints Transactions: Description' doesn't appear in Views
There is no 'Reason' field: it is named 'Description'. When you're creating a new 'Userpoints Transaction' view, you can simply add a 'Userpoints Transactions: Description' field and everything should work out fine.

Edit: I've imported your view and everything works fine on my website. Try reinstalling the User Points and the Views modules and clear caches. Hopefully that solves your problem.