Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Your problem may be with the card itself. Perhaps it is too large for the Garmin 430. How large is the (total storage capacity) of the card in question?
Did this card, or some other card, work in this Garmin device before this? if one worked, what was its total storage capacity or size ?
Since you have expressed that you do not believe I am a Garmin tech I have Opted Out of this question, in favor of a tech you might find better somehow.