I have updated and app to use the dropbox sdk version 5.2.0, before it used the 4.0.1.
The problem I have now is that when I do:
DbxRequestConfig requestConfig = new DbxRequestConfig(clientIdentifier);
Auth.startOAuth2PKCE(mContext, APP_KEY, requestConfig, scopes);
The app launches the popup dialog to allow an account, but when selecting allow, the popup response with an error saying that it could not connect, I have access to the internet and before updating the sdk this popup dialog worked fine.
Here I attach images to show the error:

