Dropbox backup error

I am try to access backup on dropbox and i given dropbox access code.
Am getting below erorr.

Traceback (most recent call last):
File “/home/frappe/frappe-bench/apps/frappe/frappe/integrations/doctype/dropbox_settings/dropbox_settings.py”, line 226, in get_redirect_url
response = make_post_request(url, data={“”: get_url()})
File “/home/frappe/frappe-bench/apps/frappe/frappe/integrations/utils.py”, line 50, in make_post_request
raise exc
MissingSchema: Invalid URL ‘None/api/method/dropbox_erpnext_broker.www.setup_dropbox.get_authotize_url’: No schema supplied. Perhaps you meant http://None/api/method/dropbox_erpnext_broker.www.setup_dropbox.get_authotize_url?

Which version of ERPNext? There were some fixed made in this functionality. Ensure your account is upgraded. Also, ensure that dropbox credentials are valid.