VSTS Build - NUGET restore error: Non-whitespace b

Question

I am new to VSTS. I want to build my solution. For some reason the Visual Studio template that was once there is no longer. So I use the ASP.Net template. Currently it is failing on the Nuget Restore;

This is set as follows;

When I go to the advanced restore options and choose V4 instead of the default V3.3, I get this error instead;

==============================================================================
Task         : NuGet Installer
Description  : Installs or restores missing NuGet packages
Version      : 0.2.31
Author       : Microsoft Corporation
Help         : [More Information](https://go.microsoft.com/fwlink/?LinkID=613747)
==============================================================================

C:\Windows\system32\chcp.com 65001
Active code page: 65001
Detected NuGet version 4.0.0.2283 / 4.0.0
SYSTEMVSSCONNECTION exists true

d:\a\_tasks\NuGetInstaller_333b11bd-d341-40d9-afcf-b32d5ce6f23b\0.2.31\node_modules\nuget-task-common\NuGet\4.0.0\NuGet.exe restore -NonInteractive d:\a\1\s\SIR.sln -ConfigFile d:\a\1\s\SIR.sln
NuGet.Config is not valid XML. Path: 'd:\a\1\s\SIR.sln'.
  Data at the root level is invalid. Line 2, position 1.

Error: d:\a\_tasks\NuGetInstaller_333b11bd-d341-40d9-afcf-b32d5ce6f23b\0.2.31\node_modules\nuget-task-common\NuGet\4.0.0\NuGet.exe failed with return code: 1

Packages failed to install

******************************************************************************

Finishing: NuGet restore

******************************************************************************

How do I fix this?

Answer 1

I assume it is a VS 2017 project, try to use Hosted VS 2017 agent instead.

Update:

Sepecify Nuget 4.0 version of Nuget restore step/task:

EDIT - From the comments below, the problem was fixed by making blank the "Path to nugget.config" parameter