Issue
Experience Site users can log in to the client portal successfully, but clicking the eye icon does not open the invoice PDF.
Even if the user has the correct and Payment Center Sites User Permissions permission set, the PDF may still not be available.
Why does this happen?
The eye icon uses the PDF link stored in the Latest Invoice PDF (fw1__Latest_Invoice_PDF__c) invoice field.
If this field is blank, the system will try to generate the PDF link when the user clicks the eye icon. This requires the user to have a Payment Center license.
Resolution
You have two options:
Assign a Payment Center license to the Experience Site user. This allows the PDF link to be generated automatically.
Attach the PDF manually - An internal Salesforce user can open the invoice record and click Attach Invoice PDF. Once the PDF is attached, the client can view it through the eye icon without needing a Payment Center license.