This isn’t certain; the argument is not deductively valid. It is abstractly possible, I suppose, that God has created us with a faculty for knowing him; for one reason or another, this faculty always malfunctions, and some other faculty created to produce some other beliefs often malfunctions in such a way that it produces belief in God. Then our belief in God wouldn’t have warrant, despite the fact that it is true. This is an abstract possibility, but not much more; it certainly seems unlikely.