SharePoint and OneDrive

ISSUE: Error message of "For security reasons DTD is prohibited in this document" when creating a Connection.

You are likely missing a required CNAME for "msoid" on your custom Office 365 domain or SharePoint site.
This can happen with Office 365 customers that previously ran on older versions of Microsoft's online offerings (e.g. BPOS).
It has also been known to affect European and Chinese hosted Office 365 customers.
To resolve the issue, add the following CNAME type DNS record to your custom domain.
Alias: msoid
TTL: 1 hour