When I updated my Windows 11 OS to 24H2, I am no longer able to log in to GRUB anymore. It just sends me into the GRUB rescue screen and it says that the file system is unknown. My guess is the update broke something.
Yes but you should read all of it of course. Live usb, chroot, then reinstall grub with a command according to platform (bios or efi).
After reinstalling update-grub, then reboot in manjaro from disk and sudo update-grub once again to add the windows entry, because it cannot see the windows properly from live usb and chroot.