So your answer is "dunno", "it's your bible".
My answer is that neither do I know why I believe yet don't pick up snakes. I guess it can still be true, if it is a sign to whom it is a sign.
Let's look at what the bible says about what the bible says.
The bible says that the pharisees asked for many signs, and they didn't believe and Christ gave them the sign of Jonah.
Who then would receive the sign of not being poisoned? The doubter or the believer?
Well, clearly, if the passage is to be taken as literally true, believers should be able to do all of these things.
So the bible is not true
if you can't see the sign? Where does it mention you, with your bunsen burner and ticker tape timer?
Does this mean I lack faith in God? Or does it mean I don't seek a sign? If I don't seek a sign yet believe, what is the excuse for those who don't believe yet seek a sign?
I'll tell you your conclusion; You think the bible is untrue, because you, like the pharisee, see no sign.