Suddenly getting "v1_retired" error

I've developed an application that sync with Dropbox. It's been working fine for the past few months, but suddenly since today I'm getting "v1_retired" when trying to get the auth token.

I'm using this to authorise the app:

https://www.dropbox.com/oauth2/authorize?response_type=code&client_id=.....

and this to get the token:

https://api.dropboxapi.com/oauth2/token

I believe this is both v2 API so I'm not sure why it's suddenly showing this error. Any idea?