Why is Artifactory not able to find my nuget packages?

If you are having an issue with installing NuGet packages:

Unable to find version ‘1.0.0’ of package ‘Some.Package’

The first test to always try is to re-index the remote repository by right-clicking on the repo in the artifact tree view.  
This will allow the remote repo to reach out and update any metadata that could be corrupted or outdated. 

You can then check the “force authentication” option in the remote repositories basic tab (Admin -> Repository -> Remote Repo).  
You can check this box if anonymous access is enabled.  
When anonymous access is enabled at the system, and the anonymous user doesn’t have permissions to the repository, we need to enable the "force authentication" option in order for Artifactory to challenge the client and ask for credentials.