Mail SBI Cards customer care asking for the rejection reason and keep escalating till they tell it.
Do not apply for any other cards till you get to know the reason. If the reason is something minor, you can apply for the card again right away after taking care of it.
Another option would be to request them to re-initiate the same application (will save you a CIBIL hit).
And your first post doesn't have to be a WikiPost.