Got my Dell XPS 9560 replaced by warranty after motherboard on previous one went bad. Took out the HDD on the new unit and swapped it out with SSD in previous unit. In the past when swapping out hard drives, if the computer didn't boot to grub, I'd just boot to Ubuntu Live USB and run boot-repair. It would detect all OSes and repair grub, etc. This time however it only detected the Ubuntu partition on the SSD, not the Windows partition. os-prober returns nothing. I can mount and read and write to Windows partition just fine from Ubuntu. Since I've simply used boot-repair in the past I'm pretty unfamiliar with EFI, grub, boot flags/required partitions, etc. Here is output from fdisk -l:
Device Start End Sectors Size Type /dev/sdb1 2048 34815 32768 16M Microsoft reserved /dev/sdb2 34816 748181142 748146327 356.8G Microsoft basic data /dev/sdb3 748181504 749150207 968704 473M Windows recovery environment /dev/sdb4 749152256 750200831 1048576 512M EFI System /dev/sdb5 750200832 1448673279 698472448 333.1G Linux filesystem /dev/sdb6 1448673280 1465147391 16474112 7.9G Linux swap /dev/sdb7 749150208 749152255 2048 1M BIOS boot Partition table entries are not in disk order.