As petsam says, you do not have a $esp in your fstab entry.
You will need to put in this at fstab
UUID=8E7F-7DF7 /boot/efi vfat defaults,noatime 0 0
Then after putting into fstab, at terminal....
sudo mount /dev/nvme0n1p1 /boot/efi
sudo cp /boot/grub/x86_64-efi/core.efi /boot/efi/EFI/boot/bootx64.efi
If the first command results in an output that states /boot/efi is already mounted, verify with
and the result must show /dev/nvme0n1p1 and continue with the 2nd, third and forth commands.
A strange case of not having a /boot/efi entry in fstab and yet having a 'manjaro' entry (/dev/nvme0n1p1) at 'efibootmgr -v'. I'm a latecomer to this topic, but reading quickly, how did that happen? I ask OP to check fstab as I did not see anywhere he did that. His grub-install does not specify that either, or did he and I missed that?
Oh.. you sent out you last post as I was typing. But ...please look into this.
@Bulaxy, fstab entry best to have '0 0 ' instead of '0 2' but either will work. I think '0 0' is better.