External Sharing won't work even with policies set correctly

Hello SharePoint Community,

I have a problem with a Microsoft 365 site that will not allow external sharing.  I have reset the permissions for the site in the site.  I have reset the permissions for the organization.  I have reset the permissions in the SharePoint Admin Center.  None of these work.  All of the other sites in this tenant are working properly.  I have also used PowerShell to reset the permissions.  I have a very frustrated client as the site in question is the primary site they use to store and share information.  Is there something I'm missing?

Thanks,

Ken