Latest update.

Thanks, moreau. Yes, Jean’s programs and files are probably intact; the immediate problem appears to be a damaged Windows shell configuration, affecting both Start and the taskbar.
We are first checking and repairing Windows system files because update error 0x80073712 suggests component-store corruption. If that fails, the next step will be testing removal of the August cumulative update.
A taskbar-layout backup would indeed be helpful, although Windows unfortunately provides no simple built-in personal taskbar backup button. Once Jean’s system is operational, we can cover a practical backup method for the pinned shortcuts and relevant configuration.