Hello William.

Thank you for reaching out to us.

A Customer in Amelia can only be linked with existing WordPress users that have the "Amelia Customer" user role. So, if you want an existing user to be linked with a customer in Amelia, you need to download the "User Role Editor" plugin, which will allow you to assign multiple roles to a single user.

Once you assign the user with the "Amelia Customer" user, you'll be able to select them from the drop-down when editing the customer.

Also, never mix administrators with any other role. That will cause conflicts between role capabilities and even though an Admin is logged in, due to the "Amelia Customer" role capabilities, they won't be able to see admin-related sections.

You can enable the "Automatically create Amelia Customer user" in Settings/Roles/Customer, so when a customer books an appointment, they are automatically assigned a WP User with the "Amelia Customer" role.