error NU1100: Unable to resolve [Some Package]

[Noggog]

Synthesis fails to build patchers, and gives this error as a reason:
error NU1100: Unable to resolve [Some Package]

[Noggog]

Caused by Empty Nuget Config

Usually this is caused by an empty Nuget file. This file tells the computer where to go to download code packages that it needs. If it's empty, it will fail to download anything.
%appdata%/nuget/NuGet.Config

It's unclear how this file ends up empty for some users, but regardless, there's a decently simple fix.

Add Nuget.org Entry Back Manually

You can usually just make sure that this entry exists:
<add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />

Here is a typical Nuget.Config file, for reference:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
  </packageSources>
</configuration>

Add Nuget.org Entry Back With Visual Studio

Lots of dev tools have ways to modify this file for you. Here's how to do it with Visual Studio:

Y8OTsY51ep.mp4

Try Again

Once the nuget file has the nuget.org entry, try reopening Synthesis and trying again

[FurriousFox]

finally, after hours and hours, the lifesaving solution!

easier would be using the command I guess dotnet nuget add source https://api.nuget.org/v3/index.json -n nuget.org