You are supposed to be able to only use one card for the safe. (Sign and Sail is not recommend). The safe is supposed to recognize one card. BUT this is how I get around it. I’ve used the same two (2) cards for 4 years now. I use old canceled Bestbuy Cards, (any 2 cards should do) but they must have the same account number on them. That way you can carry one and someone you trust can have another, incase you have to go back to the cabin at different times. They have not fail yet.
I have VOID printed on them with a Sharpie and keep them in what I call my travel box with other items that I may need or want to take with me.
Hope this helps