BUILD PIPELINE NuGet ERRORs

I am writing my first BUILD Pipeline and am having problems.

First my environment:

1) On Prem TFS/DEVOPS

2) behind firewall

3) On Prem NuGet Server

4) source is stored in TFVC

5) code is for a CRM plugin 

6) solution consists of around a dozen projects

I am trying to create a BUILD pipeline that compiles the checked in code.

i have created a Pipeline that is based on a .NET Desktop template

the first task in the agent is to Use NuGet 4.4.1/ I have selected the Default Agent Pool

this step fails with the following errror;

You are using a query match on the version string. Behavior changes or breaking changes might occur as NuGet updates to a new version.

ERR:connect ETIMEDOUT 152.199.23.209:443

##[section]Finishing: Use NuGet 4.2.0.2457

i checked: the IP address is blocked by our firewall

if i disable this step, the Pipeline fails on the next step which is the NuGet restore step. the NuGetError.doc attachment shows the errror.

It looks to me like it was not able to download the required local Nuget packages. 

I don't know how to resolve this problem. 

Can someone suggest a solution?

thanks