Hi @EuclidesG123  Dell's Product Support did not find Latitude 7400 2-in-2, but did find Latitude 7400 2-in-1.   Unless there are additional features that you want, never update BIOS just because there is a new BIOS version update (1.18.0). There are very specific installation instructions to install a new BIOS file: download file onto your laptop, verify file checksum value, plug-in powered-on ac adapter, make sure main battery has more that 20% of charge, CMOS (coin-cell) BIOS battery works, etc. When installing new BIOS file, all keyboard functions are disabled, loss of power during BIOS installation can brick the laptop.  Please install all the internal parts that have been removed. Remove all external connections to laptop, but keep the powered on ac adapter plugged into the laptop's dc-in port. Press and hold down the Fn key, press the power-on button, wait for ePSA Diagnostics to start before releasing the Fn key. ePSA Pre Boot System Assessment Dell Overview (Official Dell Tech Support) - UPDATED - YouTube Please enable ePSA option to post copy of test results to be installed on the OS(C:) boot drive.  Please share the test result of the ePSA Diagnostics (it does not test everything). For your own protection, never share your private System Service Tag or Express Service Code in this public forum.

Run an extended diagnostic on the hard drive (F12 at powerup).

When turning on the computer, repeatedly hit F11 or F12 (depends on the machine). This will go to the Dell Boot menu screen which let's you choose which drive to start up from. BIOS setup should also be the last option there.

Do not panic, the laptop is OK, and the hardware is fine! Just the SSD is unbootable/damaged.I have had the same problem after I used Aomei Partition Expert. The laptop is OK, this is important, just the security keys that the BIOS keeps do not comply with the SSD keys, which have been changed, it seems by the partitioning program.In my case I took the SSD out just to test if the laptop is OK, and boot into BIOS. After that I have managed to use an external SSD case to copy all my files from it and after that to zero all the content of the SSD. The problem in my case looked so bad, that I switched in the BIOS from AHCI to RAID, attached the cleaned SSD, and made a completely new Windows installation from a USB.It works fine now, the RAID configuration makes it use Intel drivers for NVMe, which are better.If even the the laptop does not continue the boot process, and does not allow to start BIOS with the installed SSD, then you might have to do what I was finally forced to do - completely erase/zero the 4 security keys - PK KEK db dbx These keys are in the 'Secure boot'. If you zero them, they will be generated to their defaults. It is an operation with lots of alarms, which made me frightened, but since the hardware is OK, there is nothing to worry about. In my case, my Dell G3 3500 has an Ethernet port and after the alarms asked for connection to the Dell Security Servers, and managed to make his new keys. Everything is fine now! :-)

Volume numbering is assigned by the system, so I wouldn't worry about it. I am confused about one thing. When you say PCIe drive, are you referring to M2 NVME sticks? I get the impression from your second post that you actually added a standard 2.5 inch SATA SSD. If this is the case, the new drive should definitely show up. Have a look in Control Panel- Administrative Tools-Disk Management. The new drive must be there. I would also run chkdsk to see if there are any disk errors.

For anyone still interested, I solved the issue by replacing the palmrest. The laptop is from Colombia and has a Spanish keyboard, but I usually use laptops with an English keyboard. So, I bought one from eBay, and after the replacement, it works perfectly. Now, it boots directly from the SSD, so I believe the issue was with the physical keyboard. Anyway, this laptop series has serious issues. I have three others with motherboard problems—they won’t even turn on, so sad.

I did flash the bios to the older A04 version and I still have the same problem during boot.  I found this online and I am able to enter into bios with Windows 8.  Is there any settings in the bios that can enable the boot hot key?  To enter Setup Utility: Open the Charm Bar by pressing Windows Key-C Click on Settings Click on Change PC Settings Click on General Scroll to the bottom and click on Advanced Startup -> Restart Now Click on Troubleshoot Click on Advanced Options Click on UEFI Firmware Settings Click on Restart