Repro steps:
Register-PackageSource -Name PSR -Location C:\AAD\Apps\powershell\GraphRepository\ -ProviderName NuGet -Trusted
Place files into the local repository i.e. microsoft.graph.1.10.0.nupkg; microsoft.graph.authentication.1.10.0.nupkg
Install-Package -Name Microsoft.Graph.Authentication -Source PSR
Install-Package : No match was found for the specified search criteria and package name 'Microsoft.Graph.Authentication'. Try
Get-PackageSource to see all available registered package sources.
Find-Package -Source PSR returns no results.
Other nukpg files work such as Azure AD PowerShell module