Used one of these for over 20 years without issue on XPS 400 XPS 8900 etc. Make sure its plugged into the rear USB2 ports underneath the Ethernet port. There is also software associated with this model [URL]  
Have been unable to access XPS 8500 BIOS using Microsoft Keyboard [Ergonomic] Model 1878, while the Microsoft keyboard being replaced, Model 1048, had worked OK. Noted some internet chatter suggested BIOS reset as a solution; and tried it without success. I don't fully understand the ins and outs of the BIOS settings, but I noted on internet traffic references to a Fast Boot BIOS entry having been responsible for a similar problem.  I noted no fast boot setting on my BIOS.  I have opted out of Windows 10 "Fast Start" option. Any one else had this problem with this particular keyboard? Thanks. Wayne  
XPS 8500 CANNOT ACCESS BIOS USING MICROSOFT KEYBOARD MODEL 1878