SSD dead? - Reboot and select proper boot device windows 10

One thing that happened to me once, is in my BIOS the UEFI setting got changed to legacy MBR.
It took me a while to figure it out.
That's the only thing I can offer.

If you can get into BIOS, you can check whether or not the BIOS sees the drive. Here's a link to your mobo manual, in case you don't have a copy handy: it will explain how to list drives inside the BIOS. If the BIOS can't see the drive, it may very well be dead. One good way to make sure what's what is to remove the drive from the current system and hook it up as an ancillary drive on another Windows system (I'm assuming it's SATA, right?) and then using diskmgmt.msc to determine what's up with the drive (or diskpart, or some other tool of your own choosing).
HTH,
--Ed--

Under the 'boot' tab in the BIOS I can choose [UEFI] or [LEGACY+UEFI], changing them doesn't make a difference I'm afraid.

When clicking the boot options, ex; 'Boot Option #1' to rearrange the boot order I can not see the SSD as far as I know.

When clicking the 'System Status' tab in the BIOS it lists several different SATA ports, ex; 'SATA Port 1' etc. 'SATA Port 6' says 'ST1000DM003-9Y - 100' which is what I'm guessing is the HDD.
'M.2/SATA Port 5' sticks out with the 'M.2' part and says 'Not Present' like every other SATA port listed, up to 'SATA Port 10'.

I could try hooking the SSD up to my laptop if possible, but how would I do that seeing as the SSD doesn't have a USB connection or anything similar? What do you mean by hooking it up as an ancillary drive?

Thanks again!

Edit; When booting the computer with 'Hard Drive' being selected as the boot option and it being set to [UEFI] this error or whatever it is popped up in the EFI Shell.

If it says the M.2 device is not present that's not a good sign. You'll have to pull the drive and install it in another system to see if it's working. OTOH, you can try an adapter card like this $20 item (Newegg) to make it easier to plug in and test, even on another system that lacks M.2 support (but has an open SATA port).
HTH,
--Ed--

You'll have to boot your PC from a bootable flash drive, and get into the Advanced Repair options, Command Line interface. From there you can run diskpart. But if the BIOS doesn't see the SSD, neither will diskpart.
HTH,
--Ed--

Le SSD est mort. Vive le SSD!
I guess it's time to buy another one. Look to Les Tokar's excellent website TheSSDReview.com or Tom's Hardware for good recommendations on replacement units.
HTH, and good luck with the rebuild. Hope you've got a usable backup at your disposal...
--Ed--