Failed cert on Package Manager installs

I have randomly started getting errors involving the package manager and downloading/retrieving certain package related installs. No changes were made to my machine or Unity when this started happening.

The error occurs when opening a project which needs to be rebuilt (packages resolved), and when I try to install something through the Package Manager.

The error on project startup:

An error occurred while resolving packages: One or more packages could not be added to the local file system:

com.unity.mathematics: unable to get local issuer certificate
com.unity.render-pipelines.high-definition: unable to get local issuer certificate

the error when attempting to download a package:

Cannot perform upm operation: unable to get local issuer certificate [NotFound]
UnityEditor.EditorApplication:Internal_CallUpdateFunctions()

This is happening in Unity 2018.3.11f1 (and various other 2018.3 versions). Sometimes I can download a package depending on the version I choose, but it seems I can never get the exact ones I need, or open the project that requires them.

I am using a work machine, and everything has been working fine up until now, and nobody else at the company is having the issue, so I don't think it is related to some firewall/proxy setting. Also it seems to work without issue in 2019.1, but the project isn't using 2019.1 yet, so that isn't an option for now.

Any advice would be appreciated.

Thanks,

-Jordan

UPDATE: The issue started spreading throughout the company even more, another person got IT involved and they white-listed some specific things necessary for the Package Manager. As for now it seems to be resolving the issue. (However, I am still baffled by how this issue wasn't happening in different versions of Unity, and only 2018)

 

Apologies, but I have no idea where to access this and use the command line option. Since there is a warning about affected other node applications I assume this is not within the Unity Editor.

Do I have to acquire some sort of Node.js tool (currently looking at the Node.js runtime), or does it exist as a file in Windows somewhere?

 

Having followed this, there is no information on how or what to put into the environment setting.

I know the command line is

NODE_EXTRA_CA_CERTS=file

but what is "file" ? because entered in like this, it does not work. It also mentions: When set, the well known "root" CAs (like VeriSign) will be extended with the extra certificates in file. The file should consist of one or more trusted certificates in PEM format.

Am I supposed to replace "file" with a directory address containing a certificate? If so, I am still unclear on what certificate I am supposed to be using, or how to even acquire one.

EDIT:

I attempted it with just NODE_EXTRA_CA_CERTS which did not seem to resolve any problems. I would also like to point out that only some items in the Package Manager cause this problem. So it seems I am capable of accessing the Package Manager and downloading/installing packages, just not certain ones, specifically the High-Def Render Pipeline (which is what i need).

This also doesn't happen with 2019.1 (which according to the work around is meant for anything before 2019.2) So why would my 2019.1 function normally?

 

Bit of a late reply on this, but figured I would add it. The issue started spreading throughout the company even more, another person got IT involved and they white-listed some specific ports necessary for the Package Manager. As for now it seems to be resolving the issue. (However, I am still baffled by how this issue wasn't happening in different versions of Unity, and only 2018, assuming it was a firewall problem)

 

This is still happening in 2020.1.0a13
I just wanted to download a new package and got this error.
since i know that my company network is has a strict firewall, i tried the public wifi to try and download the packages and the error was gone.