Unable to Change Portal Type from Blank to Customer Portal in Dynamics 365

What’s happening?

After creating a Power Pages site using the blank page template, other templates (such as the Customer self-service template) cannot be applied. 

Reason:

Once a site has been created, a new template cannot be applied. 

Resolution:

To apply the desired template to a site, a new site must be created.

Refer to the resources below for more information: 

• Dynamics 365 templates | Microsoft Learn
• Create a site with Power Pages | Microsoft Learn