Lots of random weirdness for me trying to use mine. Most recent example was trying to checkout as a guest on Little Caesar’s app. Kept declining my Apple Pay transaction without telling me why — changed the email and it worked.
There’s only been a handful of times I’ve used it, maybe 12? At least a few of those times it wouldn’t even let me submit it saying it was an “invalid email”. Couldn’t even get past the validation.
Any idea if using a custom domain would have worked better here? I wouldn't be surprised if some places only accept email addresses from a small set of "known" providers