I think, somehow during a Windows Update your Boot environment got corrupted. Can you please boot into Windows, then open a elevated command prompt (right click on “Command Prompt”, then select “Run as Administrator”). Then run:
mountvol X: /s
dir X:\*.efi /S
Can you then please post the output here - this way we know if the boot loader for EOS are still on the EFI system partition. After that we can work out the next steps.