@Guswah:
As first step you have to insert the NVMe module into the original "pure" BIOS file. If the manufacturer of your mainboard just offers a complete BIOS Installer (as *.EXE file), you have to extract the real BIOS file from it.
If you don't know how to do it, please tell us the manufacturer and the model of your mainboard and give us a link to the Installer.

@Guswah:
Since the question "How to extract a certain DELL BIOS" has nothing to do with the topic of this thread, you should better have a look into >this< specific thread, where you can find some solutions. If you have any additional question regarding the extraction of the "pure" BIOS file, please post it into the linked thread.

@Salvatore21872:
Welcome to the Win-RAID Forum!
I do not modify any BIOS upon request. That is why I have written the related detailed guide about how to do it.
The modification of an ASRock AMI IV UEFI BIOS and the flashing of it (after having removed the capsule via the UBU tool) is very easy.
Good luck!
Dieter (alias Fernando)

@scorp:
Since the correct modification of your specific BIOS seems to be very tricky regarding the Pad-file, I have attached a BIOS, which has been modded by me on the basis of the original BIOS without touching the related Pad-file. You can flash this BIOS at own risk.
Don't forget to rename the modded BIOS and to flash it a proper way.
After the successful flash of the modded BIOS you shold see a Disk Drive named "PATA" or "PATA_SS" within the "BOOT" section of the BIOS.
Good luck!

@scorp:
Thanks for having tested the BIOS, which had been modded by me. It is a pity, that it didn't work either.
Questions:
1. How did you flash the modded BIOS?
2. What makes you so sure, that the flashing procedure was successful?
3. How is the NVMe SSD connected to the mainboard?
4. Do your BIOS settings allow to boot off devices in UEFI mode?
5. How many other HDDs/SSDs are running within your computer and to which ports are they connected?

Zitat von scorp im Beitrag #4775

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I'm still waiting for m.2 to SATA Adapter to check if the drive is working at all.

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@scorp:
Thanks for your additional information.
To exclude, that the NVMe SSD is not detected by the BIOS, because the related PCIe slot uses the same data transfer lanes as any of the SATA ports, I suggest to temporarily unplug both SATA connected Disk Drives and to look, whether the BIOS detects the NVMe SSD under these conditions.

Zitat von scorp im Beitrag #4779

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I think, I didn't experience such a strange behavior before. May be, this is somehow influenced by the modified BIOS.....

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@scorp:
Since I am pretty sure, that the latest one of the modded BIOSes fully supports booting off an NVMe SSD, I only see 2 possible reasons for your failure:
a) The BIOS has not been successfully flashed into the BIOS Chip of your computer.
b) Your tested M.2 SSD either doesn't correctly work or doesn't support the NVMe protocol (by the way: Who is the manufacturer and which model is it?).
To exclude the possibility b) it would be a good idea to test the function of the M.2 SSD within another computer, which natively supports NVMe.