M2 Nvme disk inserted in PCIe adapter does not show up

Open Disk Management, right click on the new drive, select wizard to create a new simple volume.

@Chino de Oro

The lexar disk does not show up in disk management​

Provide the specific adapter model, which PCIe slot it was being installed (use motherboard pix or slot # imprinted on mobo for identifying), did PC set to AHCI operation mode.

@Chino de Oro​ 

PCIe x8 slot 2 above the blue x16, and yes the AHCI is turned on.

Move the adapter w/ SSD and test with slot 4, PCIe x16 slot.  

@Chino de Oro​ 
The same happens

Open elevated command prompt, type diskpart, then type list disk.  Can you see the Lexar drive and its capacity? 

If yes, notice the disk numbering of Lexar.  Then type select disk x (replace x with the disk number of Lexar).  Then type clean.  Be very careful at this step as it can wipe a different disk if you made a mistake.  The clean function should clear off any partitions and reset Lexar drive to raw state.

Now, try to open Disk Management again.  You will see a message to initialize the Lexar disk and it's ready for partitioning.

If no Lexar disk in diskpart, the issue may be with the adapter or the Lexar SSD.  Troubleshoot by testing with a different adapter. 

Any picture of actual setup or any information on the adapter you can disclose?  That would help to spot problem.

@Chino de Oro

The lexar does not show up in diskpart​.
I don't have another adapter :/ 

https://hurtel.com/en/products/ugreen-cm465-pcie-4-0-x16-to-m-2-nvme-m-key-expansion-card-black-136196.html

https://www.lexar.com/product/lexar-nm790-m-2-2280-pcie-gen-4x4-nvme-ssd/

Thanks for the additional info.  Something isn't right as the report for free space are different between Disk Management and diskpart.

If the adapter is eligible for return, get with the seller for option.  Otherwise, next troubleshooting step is testing with a different NVMe SSD. 

Because you have indicated that you tried most of solutions from the internet, it's difficult to know which you have not tried to suggest.

While working on the motherboard, remember to give your system a new coin cell battery as part of a low cost maintenance.  Reset CMOS using jumper, then adjust BIOS settings to match with hardware setup.

@Chino de Oro​ Ahh... I entered the Manage Storage Spaces and formated disk and now works, thanks forhelp!

Glad to hear the drive is now working.  By default, the T5810 supports bifurcation natively.  NVMe SSD can be used on PCIe slots and be recognized by BIOS automatically.  Any issue with storage recognition would have caused by hardware installation and storage setup.