I've been driving myself crazy trying to fix this issue. I'm also a AT&T Fiber user and finding this thread I was able to solve the issue by using a VPN.
I used Toms guide to determine which is a good free VPN. I used the following link:
https://www.tomsguide.com/best-picks/best-free-vpn
I choose to go with Proton VPN since it was free and had good reviews, I did not try any of the others.
Using the above VPN I was able to immediately log into P99. I've been using it for about an hour without any issue. My ping is between 88-92 which isn't ideal but for EQ is probably good enough.