Have you partitioned and formatted the drive?  If not, Windows cannot see it. [URL]  
I have installed on the second slot additional SSD Type: WD Black SN850X 1TB PCIe Gen4 NVMe M.2 2280, Read:7,300MB/s, Write:6,300MB/s SSD(WDS100T2XOE) The storage can be seen in BIOS as recognized in the second slot and is "ON" , but in Windows 11 is not visible - does NOT show and can not be accessed or used.  In specifications says that DELL G15 5511 support Gen4 , but actually not working- it is not visible in Windows11.  Is there anything can be done to fix that problem?
G15 5511, not working with WD Black SN850X Gen4