Assume that you have a Master Data Services (MDS) solution in Microsoft SQL Server 2014 and the solution uses the NT LAN Manager (NTLM) Authentication protocol. When you try to connect to the MDS solution by using MDS Add-in for Excel, you receive the following error message:
The HTTP request is unauthorized with client authentication scheme ‘Negotiate’….401 error
The issue was first fixed in the following cumulative update of SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. We recommend that you download and install the latest cumulative updates for SQL Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.