Registering the web adaptor via a command line using https fails with the error message, "Unable to connect to WebAdaptorURL", if the IIS Instance has disabled TLS1.0 as an accepted server TLS Protocol.

Solución alternativa

1. This only fails using the command line registration, this will work from the browser without issue.
2. Save the text file found here as tlsupdate.reg. https://downloads.esri.com/resources/enterprisegis/ArcMapPost104TLS.txt
   1. Double click the .reg file to update your registry.
   2. The registry entries above enable TLS 1.2 as a default for all applications utilizing the relevant .NET version – This is a desired state for most organizations, but if there are any issues, the user can just remove the registry entries.

Pasos para reproducir