1 month ago, I installed first Windows 10 on my nvme ssd and then after I got my second nvme ssd, I removed the nvme ssd with Windows 10 and installed Fedora 34 on the second nvme ssd. After that I plugged in the first nvme ssd with Windows 10 and I could boot either in Fedora 34 or Windows 10 without a problem.
After a while, booting in Windows 10 is not anymore possible from Grub Menu, only going to Uefi System Settings, Boot and then selecting Windows 10.
In Fedora 34 I have the following partition:
/efi (/dev/nvme0n1p1) (UUID 8363-EC93)
/ (root partition encrypted)
In Windows 10:
efi partition (/dev/nvme1n1p1) (UUID 20E3-31D9)
local disk c
local disk d
microsoft windfows recovery environment
Selecting in boot menu Windows 10 gives the following error:
There is often a conflict when you have 2 different efi partitions. When you removed one drive while installing fedora you forced the installer to create a second efi partition on the second drive and I am surprised that grub was even able to boot windows initially since it had no reference to it during the initial install.
You can use efibootmgr -v to see what the current boot order is.
You can also use the -o or -n options with sudo to set the boot order or next boot choice.
I would strongly suggest that you merge the content of the two different efi partitions into the one on the windows drive then delete the one on the fedora drive after you have verified that both OSes boot properly that way.
This link might help.