This message has appeared when we tried to authorize a newly created DropBox account through oauth2 api:
"This app is unable to link additional users because it has been frozen pending review."
That appears right after the authorize request is sent:
https://www.dropbox.com/1/oauth2/authorize?...
I'd like to mention the message appears only for newly created accounts but using an old account works just fine.
I also can see my app has been added to Apps linked list of that account.