I have just built a new PC, and I booted it up "EFI Shell version 2.31" came up on my screen. I googled it and apparently you just needed to put a HDD in. I already had one in. I took it out and i got the same error. So my computer doesn't detect my HDD. The thing is my old computer which I used maybe 5 hours prior to building the new one worked just fine with the HDD. I have never built a PC and the SATA port looks weird to me. It has no rivets or pins, only a plastic hole. The SATA cable was also very loose on the HDD end but not the motherboard end. Please help me with this and thanks in advance.
Are you able to get into your BIOS and see if it detected there? Make sure the SATA cable is connected nice and tight and in the correct direction, also the power connector as well (double checking never hurt).
Also may want to update your BIOS if possible, may not be the post probable solution, but better to try.