I’m following the guide, but I can’t find the ‘Existing subscriptions’ button

It sounds as though you might need to update the app by visiting your app store and clicking on ‘Updates’. You should then see the button. 

Here’s a handy link for Android devices (using Google Play Store to download apps):

https://support.google.com/googleplay/answer/113412?hl=en-GB

Here’s a handy link for iOS devices (using Apple App Store to download apps): 

https://support.apple.com/en-gb/HT202180 

last updated: May 29, 2020