M14x R2, no bootable device, help :(

Hi all, need some advice!

I have purchased a 2012 Alienware M14x R2 (eBay, I am currently off work and wanted a project to keep my mind busy). It was described as having no HDD or power cable, and they didn’t know if the battery was okay as they had no power cable to test it. I literally fix up PCs and laptops for fun, so thought why not? I now have a headache! 
I plugged in my SSD (500GB Crucial 2.5 with Windows 10 preloaded). Plugged the laptop in and allowed it an hour to give it a bit of juice. When I turned it on, everything came on except the screen, and the disc tray made a clicking noise and it turned off two seconds later. Another two seconds later it turned itself back on, and then let out numerous beeps which were very loud! It was doing 5 beeps in a row, which I understood to be the cmos battery so I went ahead and took the whole thing apart and replaced it with a brand new one.

Following this, the laptop still does the strange turning itself on then off, then back on. I then get the Alien screen for a second and then it immediately goes to “No bootable device - please restart system”. I have gone into the BIOS and the SSD is detected, but I’m not able to go into the boot order menu to change anything, it won’t let me?! It was set to RAID, I changed it to ATA and AHCI but when restarting these had been automatically been changed back to RAID.

I ran the post boot diagnostic test and it completed with no errors, but still wouldn’t boot my SSD. I switched it out for an old HDD from a laptop I know works perfectly, with Windows 7 on. Literally exactly the same thing as above. Ran the diagnostics on it, same again, no error but still says “No bootable device” and won’t let me change the boot order.

I tried plugging a USB loaded with Windows 7 and then Windows 10 (for the different drives respectively) to see if I could work around this way, but no joy here either.

I don’t have a Windows disc for the drive but could burn one potentially, just don’t know if I’m wasting my time?

Any advice is greatly appreciated as hairs are being torn!

It is i7-3610QM, 4GB RAM, NVIDIA GFX. It has a service tag, but no asset tag. It’s the first time I’ve seen an Alienware with no asset tag.