Well, if DropBox prompts you to create new account, I imagine, you're most likely not logged in.
If you reject the prompt, you're still not logged in and Joplin proceed thinking you didn't setup a sync target (runs locally).
Watch out for the "Log In" button at the dropbox user creation prompt, try using it to log in
It redirected me to a page, which asked me to confirm Joplin in Dropbox.
The Email address there was mine.
Yes, this page asked you to confirm Joplin permission to use the cloud and supposed to give you a code to input in the text box (2nd step on your image). Did you see the code? Did you submit it?
Yes I did and yes, that seemed to work our fine, it caused no error and directed me to the casual start view.
So is your problem solved now? And if so, could you indicate the solution in the thread you opened?
It might be useful for people searching similar issues
No, it is, as initially stated.
I cannot see any change to the default view, besides some account details at the 'syncing' button.
Other than that, its no different to a default Joplin.
Could it be that your notes are not in the root of Dropbox but in a folder, say /Notes/ or something?
So far what I know is that the sign in to Dropbox from android was seemingly successful but no notes were fetched.
I assume it might be because the notes are not stored in the root of Dropbox but I have no idea how to configure Joplin to read notes from subfolders of Dropbox.