Maybe it only kicks in at a certain amount? I usually wait until I want to order enough to get free shipping, so I’ve never ordered under $75. It’s odd that it shows up randomly! Maybe email them. The one time I realized it didn’t show up, they emailed me back with a store credit for the 10%.
I had 122.00 in the cart and no discount lol. I have emailed them, not a real big deal, it is just the principle of the thing.