I’ve seen this one about a lot and yesterday it happened to me. Windows 10 has a thing about fonts, but it seems it only has a thing about fonts when it isn’t in control via… the FIREWALL! If you’ve disabled the firewall service then you can no longer install fonts. It’s stupid (there’s a shock), but just re-enable the firewall and your fonts should be good to go.
Some people also still find this doesn’t work. Due to the nature of Windows 10 and the fact it loves to use MS accounts (Hotmail, Outlook, Live, etc) to sign in that will also sometimes play with your UAC admin privileges. Yes, I know, it shouldn’t. Theory vs Practice and all that jazz. If you’re still having issues then create yourself a local account and give it administrative privileges (hint hint: http://windows.microsoft.com/en-gb/windows-10/create-a-local-user-account-in-windows-10) and give it another whirl with the Firewall on, you should be golden.