help understanding token_access_type offline

You can find more information on this migration in this blog post. That change, where Dropbox will no longer return new long-lived access tokens, is planned for September 30th, 2021.

Going forward, any apps that need long-term access should instead use short-lived access tokens with refresh tokens. An app can use a refresh token to get new short-lived access tokens for the user whenever needed, without further manual user interaction. An app gets a refresh token by requesting "offline" access.

That linked example shows an updated example implementation of using the OAuth flow via the Dropbox Python SDK to request offline access and get a refresh token, which is available in the "oauth_result.refresh_token" variable there. That enables the app to get long-term access without having the user manually re-authorize it repeatedly.

Refresh tokens can be stored and re-used for any particular app-user pair, just like long-lived access tokens could. Note though that, also like long-lived access tokens, refresh tokens can be revoked by the user or app at any time.