Suunto announced that their old Movescount app will no longer be supported and they are going to use a new app instead:
https://www.suunto.com/en-gb/Content-pages/digital-service-transition/
Therefor Suunto offers an interface only to their new app. To connect PerfectPace with Suunto you first have to install the new Suunto app and create an account. With this it will be possible to sync activities with PerfectPace.