Some users have reported difficulty installing Docrio in a Sandbox environment. This is likely due to an issue with the Remote Site Settings, where the Remote Site URL defaults to the production URL instead of the URL for the Sandbox.
Click the Setup Cog > Type "Remote Site Settings" in the Quick Find bar > Click Remote Site Settings
Click Edit beside 'Litify_Files_Token_Management' > Change the 'Remote Site URL' from 'https://login.salesforce.com' to "https://test.salesforce.com" > Click Save
Continue installing Docrio following the steps in the Docrio Configuration Guide.