How about On ne peut pas refuser ce cadeau?
"on" would be "we" (we can't refuse this present).
In this sentence both "tu" and "vous" should work as there is no context as to who "you" is.
Why would "On" not be understood as "One"?
pourquoi on ne peut pas écrir : Tu ne peux pas refuser DE ce cadeau?
"Ce cadeau", c'est un COD, pas un COI, n'est-ce pas ?
Almost sounds like a threat
Why not: "Il ne faut pas refuser ce cadeau?"
Because that means "must not" not "cannot".
Thanks. There's a BIG difference between "can not" and "must not" and if you're serious about learning French, it's VERY important to know the difference.