This usually means that your .\sitecore\user.json file is not yet in your folder structure. I had this happen to me when I initially downloaded a project and tried to get things up and running from what is in source control. Typically, the user.json file is user-specific so is not in source control, therefore would be missing after your first download of a new project.
You can trigger the creation of the file by executing a fully-specified authentication with the
allow-write parameter set to true. For example:
dotnet sitecore login -a https://my-id.sc.localhost -h https://my-cm.sc.localhost --allow-write true
NOTE: Make sure to alter the host names above to the ones that are applicable to your installation. The first host name is the IdentityServer instance, the second is the Content Management instance.
You can see more details in the official documentation: https://doc.sitecore.com/developers/100/developer-tools/en/log-in-to-a-sitecore-instance-with-sitecore-command-line-interface.html