What causes the pinned folders in Quick Access to vanish on Windows 10?

You are re-pinning folders in Quick Access, but the pins disappear after a restart or update while the default folders remain. Confirm that each target folder still exists and is reachable, especially if it is on removable storage, a network location, or synced storage. Pin one affected folder, restart the PC, and check whether that one survives. If no pins persist, open File Explorer Options, review privacy settings, then use Clear to rebuild recent and frequent history before pinning a test set again. Do not delete hidden shell or destination files while troubleshooting, because that can remove the list without fixing the cause. Test a new local Windows account: pins that remain there point to a problem in the original profile rather than the folder itself. Windows does not provide a supported lock or automatic backup feature for Quick Access pins, so keep important paths documented until the cause is isolated.