What NuGet Could Not Find
NuGet could not find the requested package ID in any enabled source, which usually means the wrong feed, mapping, name, or credentials.
Validation
Re-run the failing command and confirm the original code/message is gone, and confirm expected artifacts or outputs exist (packages restored, build/publish succeeds).
Confirm the exact package you asked for
Confirm the package ID exists in the intended feed, check sources and mapping with dotnet nuget list source, update NuGet.Config, and fix auth (PAT or credential provider) then rerun with dotnet restore.
Why It Was Not Found
Usually this comes down to wrong package ID or wrong feed configured, private feed auth failed, so the package isn’t visible, or source mapping or policy prevents using the feed that contains the package.
Prove the Source Resolves Correctly Now
dotnet restore succeeds without NU1101, and dotnet list package shows the dependency resolved.
Typical Output
error NU1101: Unable to find package MyCompany.Internal.Package. No packages exist with this id in source(s): MyPrivateFeedMechanism
NuGet queries each enabled feed for package metadata by ID. If every feed reports no such ID, or cannot be queried, restore fails with NU1101.
Avoid Version and Source Drift
To prevent this, commit a repo-scoped NuGet.Config with sources and mapping, and validate restore on clean machines and agents instead of relying on warm caches.
Docs and source code
NU1101 message template
User-facing message template. - GitHub
<data name="Error_NoPackageVersionsExist" xml:space="preserve">
<value>Unable to find package {0}. No packages exist with this id in source(s): {1}</value>
</data>
<data name="Error_NoPackageVersionsExistInRange" xml:space="preserve">