We are retrieving the long lived access token from facebook fine, however we need to renew this token automatically so that it does not expire every 60 days.
Reading the documentation it says you can only exchange short lived tokens using the endpoint.
As we don't have the short lived token, how can we do this server-side without having to manually re-authorize every 60 days?
it is not possible, to extend token endlessly. See Scenario 4 here https://developers.facebook.com/roadmap/offline-access-removal/: