Haven’t been able to use Amex online chat for months. I’ve harassed them on social media (which doesn’t go very far), and they’ve emailed me just saying “it’s definitely working”
You’ve probably tried different browsers/allowed pop ups and found it still doesn’t work, but I have used chat 4 times last 2 weeks and it’s worked fine for me. Quality of their CSRs manning the chat is a different matter...