Icloud sign in arrow not highlighted

I cannot log into my Icloud on my PC because on the sign in screen, the arrow is not highlighted. My login and password are correct, but the system will not allow me to press return or click on the arrow to enter into my account. I have no problem signing in on my Iphone 6- can anyone please offer a suggestion as to what the problem may be? I'd like to go into my Icloud account on my PC, so hopefully this can be resolved. Thank you.