When attempting to log in to ArcGIS Pro with an ArcGIS Enterprise Named User license, the login fails, and returns the following error message:
Error: ArcGIS Pro failed to connect to the License Manager for your Licensing Portal. Please contact your organization's License Administrator to ensure that your ArcGIS License Manager is running and accessible.
The hostname and port number for ArcGIS License Manager are not defined in Portal for ArcGIS. This does not allow Portal for ArcGIS to communicate with ArcGIS License Manager, and prevents it from validating all Named User licenses. Refer to ArcGIS Pro: Named User licensing in ArcGIS Enterprise for more information on how ArcGIS Enterprise Named User licenses work.
To resolve the issue, perform the following workaround.