Are you patched correctly? Have you turned it off and on again? Do you meet minimum specs? Does your PC meet minimum specs? Are you in the right thread? Have you tried the helpful guys at Ubi.com? Have you followed the tutorials? What mods are you using? Are you using Commander? If so have you used the GWX/Commander config thingy? What resolution are you using? Is your keyboard plugged in? Have you removed program, cleaned registry, and reinstalled? Have you pressed every key on the keyboard?
Is it working yet?
