I have a NUC5i7RYHR with a 275 Gb M.2 SATA and a hybrid 2.5 inch SATA drive. I recently gota 1 TB SSD HD. I cloned the OS (Windows 10) to the new drive from the M.2 SATA. I had to play some games to get a uefi partition on the new drive. I installed the new drive and removed the other two drive. The system will not boot from the ssd. It will only boot with both drives in place. Is there a way to set up the box so that it will boot from the SSD and not require the M's SATA drive?
It sounds like the boot structure for Windows OS didn't get set up properly for your new drive.
What did you use for the disk cloning? Also, what is meant by "play some games to get a UEFI partition on the new drive" ?
You may need to run the Microsoft "bcdboot" utility to make your new drive properly bootable.
There is also another way to choose instead of discarding M.2 drive: