Windows Update error 0x80070643 means a .NET Framework or MSI-based update component failed. Here's what causes it and how to fix Windows Update.
A .NET Framework or Visual C++ component that the update depends on is damaged.
Next step: Download and run the .NET Framework Repair Tool from microsoft.com. Restart, then retry Windows Update.
A deeper installation database corruption is blocking the update.
Next step: Open Command Prompt as administrator and run: DISM /Online /Cleanup-Image /RestoreHealth — wait for it to finish — then run: sfc /scannow — restart and retry.
A recently installed program replaced a shared component with an incompatible version.
Next step: Uninstall the most recently added program and retry Windows Update. Pay attention to programs that install their own version of .NET or Visual C++.