While getting access_token for my app, error(500) occured.
Please let me know the reason.
I'm developing an app using dropbox cloud.
Until now, there was no problem. But since this error occured, I can't go on developing.
Please help me.
See https://status.dropbox.com/. I would wait until the status shows that Dropbox is fully working, and then try again.
dropbox state is "running normally", but my app is still not running normally
I'd say give the recovery a bit more time. It's very likely that the error you're getting is related to this issue.