Why does my Apple Pay not work for online purchases?

I have my card setup in my wallet. And Apple Pay always works when I use it in store. However, as of lately, when I try to use it for online purchases (on websites that have the little Apple Pay button, so I know it’s supported) it always says “payment failed”. I know I have sufficient funds, and it always worked before. My last transaction was 2/2/23 but since then it always says “payment failed”. I’ve checked all of my settings and they seem correct. I haven’t made any changes to it so not sure why it would stop working all of a sudden.