This project references nuget packages that are missing

I'm trying to start a new project with a template provided by oneof my colleagues. When I load the template I try to restore the nuget packages but it says 'All packages are already installed and there is nothing to restore.' So I then try to build but get the following error:

This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them. The missing file is ..\packages\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets.

and it references the following line in the csproj:

NewUserCreation C:~\repos\NewUserCreation\NewUserCreation.csproj => line:1319

In the csproj the line in questions shows:

<Error Condition="!Exists('..\packages\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets')" Text="$([System.String]::Format('$(ErrorText)', '..\packages\Microsoft.Bcl.Build.1.0.21\build\Microsoft.Bcl.Build.targets'))" />

I'm not really sure what's going on as I can't see anything obvious. Any advice would be very welcome Thanks.