Unable to create an initial administrator account after installing Portal for ArcGIS on a machine

Description

After installing Portal for ArcGIS on a machine and attempting to create an initial administrator account, the portal web page shows the initial administrator account has been set up, as demonstrated in the image below.

Clicking 'Sign In' on the ArcGIS Enterprise portal returns the following error:

Error:   
Unauthorized

Cause

The arcgisportal folder of a previously installed Portal for ArcGIS deployment has not been removed from the machine. The initial administrator account of the previous deployment is stored in the arcgisportal folder, preventing the new Portal for ArcGIS deployment from creating a new initial administrator account. When the Sign In option is clicked, the new Portal for ArcGIS deployment returns the error message due to login attempts using the unauthorized initial administrator account information.

Solution or Workaround

Delete the arcgisportal folder on the ArcGIS Enterprise portal machine before creating an initial administrator account on the portal web page.