Prettier not working for Create React App with Typescript?

With a normal Create React App when I've added Prettier it's been easy to set up. Under Tools / File Watchers I add Pretter with the default settings. 

However when I start a Typescript project with Create React App with the following: 

yarn create react-app my-app --typescript 

Then I can't get Prettier to work. On the settings page I get an error saying "No files in scope". Im not sure if this is the cause of the issue?