You might have to wait a bit longer. I’m pretty sure the Apple Card doesn’t support single use or fixed amount numbers. You can generate a new number in the app, but that’s not quite the same thing. I think that also invalidates your existing number, although I haven’t tried it yet.
I’m also not sure if the number in the app is the same as the number embedded on the strip on the card. But overall, it’s a vastly improved experience compared to other cards I have.