To reset the Microsoft Store app in Windows 10, do the following. Open Settings. Go to Apps -> Apps & features. On the right side, look for Microsoft Store and click it. The advanced options link will appear. Click it. On the next page, click on the Reset button to reset Microsoft Store to default settings.
A full flash update will flash the bootloader, but reset protection may use variables stored in RPMB. "One or more operating systems may include a replay protected memory block (RPMB). The RPMB may include, as examples, a bitlocker key, virtual smartcard key, app store certificates, DRM keys and corporate certificates.