You must check that you have cse enabled in bios, the function is also called legacy support, you are dual booting an UEFI os designed for gpt partition on same drive as a legacy os made for mbr, that's not always straight forward
Just deploy W10 on a native vhd partitioned as MBR, add it to bcd using bootice or easybcd, and reboot. No need to complicate your life using ISO, Rufus, Ventoy or whatever
Winntsetup is a great tool that make even simpler the already simple instructions I wrote above, especially for people scared by a couple of command line commands, but has its value also for power users.