ERR_CONNECTION_TIMED_OUT when redirect user to redirect uri
Are you getting this error after the user authorizes the app and Dropbox redirects them to the URI specified in the redirect_uri? If so, it sounds like the error is occurring on your site, so I would check the logs for your server to see what the issue is (and that the URI itself is correct to begin with).
The app approval page does not appear. The user is redirected to redirect uri directly and the redirect uri looks like https://temp.tilecleaners.com.au/dropboxTest/dropboxAuthFinish?state=r64D6Ha6UlKRisYmKWf9eg%3D%3D&code=wX8v1aOdQSAAAAAAAAAAY_JyFIOfsaQHtzRumwLaQHI
Yes, if the user has already authorized the app previously, the app authorization page may automatically redirect them to the specified redirect URI.
In any case, it does seem the timeout is occurring on your site https://temp.tilecleaners.com.au, so I'm afraid I can't offer much more help from our side. You'll need to investigate why the connection to your site is timing out. (As a test, I did try browsing to just https://temp.tilecleaners.com.au and it is not responding.)