maybe sda1 was a fat32 /boot/efi for windows , it has be formatted by ext4 ,
you will need a USB iso windows for repair if this was the case
with gparted change , sdb1 for flag boot & esp only (remove legacy_boot ) ,
for sdb2 remove flag boot & esp
missing entry boot in EFI you will need this under chroot
sudo manjaro-chroot -a ( type 1 if only one line 0 )
efibootmgr -c -d /dev/sdb -p 1 -L "Manjaro" -l "\EFI\Manjaro\grubx64.efi"
efibootmgr -v
exit ( for end chroot )