Edit: Fixed it by logging into my products page. Will get back to you if it happens again (session timeout?).
Love that we get email notifications now, but it seems I can't reply to comments.
Opening up the devtools for
https://store.kde.org/p/1100894, shows that when I hit Send, it tries to prompt for my password like when I try to visit my product page (since it show's I'm still logged in).
Here's the devtools network response preview: