Hi, I understand how frustrating this kind of issues.
Since the issue started due to a Virus and you have done a system restore there might be issues with corrupted Windows system files. That is why it is showing in accessible boot device. If you have Windows 10 installation media, it can be fixed by inserting the installation media (Windows 10 bootable DVD or flash drive) and then performing the operating system repair. Sometimes a clean installation of Windows is needed.
I can help you with fixing this issue by giving step by step instructions.
If you have Windows installation media , kindly let me know