Thank you for answer. Actually, this happened long time ago. As you known, edge is using edg in UA string. But when I change Ua string to edge then it is working fine with Facebook login and also prompt Security Key when I login. But with edg UA string, it is opposite.
Sorry, what do you mean? You mean If I delete edg in UA string? --> I use chrome UA string instead of classical UA string of EDGE then prompt for Security key appear normally./.
That makes sense, I'm sure they're not sending the right page if they think we're Edge Classic. As long as you can get it to work, that's what matters!