I believe it originally came with Windows 7, but I'm not sure about your specific model. As such, I'll guess it may have to do with the driver for either the motherboard or the keyboard itself. Try visiting the Dell website and see if there are updated Windows 10 drivers available for your computer model's keyboard, or even the motherboard/chipset. If so, download and install them. It may even need an updated BIOS. Check for that also. The problem with many Windows 10 upgrades is that they may not get all the hardware drivers correct for each and every system. As users, we need to check to make sure.

Hope this helps.

Grif