My SS cards do start with 409758. However, my Vanilla Visa gc (bank is Sutton) does not start with that prefix. However, I'm pretty sure that I successfully used Sutton cards in Wally before. Are you saying that only Incomm cards that start with 409758 work?

I'm not sure how you can say that Vanilla gc were never an issue in Wally. I am sure that people posted years ago that they did not work for more than $50 or $99 at a time. You don't remember those days? Then 1 day, I read about SS cards working there so I (wrongly?) assumed that Vanilla gc still didn't work there.