The organization name in the URL is not valid. To determine the organization name, start the Dynamics 365 Web application ...

The organization name in the URL is not valid. To determine the organization name, start the Dynamics 365 Web application as a user who has the System Customizer role. Click Settings, and then click Customizations. On the Customizations page, click Developer Resources. The organization name is displayed next to the "Organization Unique Name" label.