While I can't comment on you account directly (you'd need to submit a support ticket for more direct info), we receive very limited information on why a card is being declined. Generally, the only info we see is "insufficient funds", "CVV is incorrect", or "card number is incorrect".
If you're card is being declined and you're sure all information is correct, and you're sure that there's funding available, I would call the issuer and see if they can provide more info.
That said, when it comes to initial setup, a preauth charge is generally used to verify the card has at least some degree of funding (though we don't have access to or know how much or what your limit is -- just to clarify).
These charges generally show as pending and are then removed as they are not actual charges to your account -- they do, however, result in the funds showing as in-use until the hold is removed.
Generally, a preauth is $1-$2.