Configuring port forwarding on AT&T router models using "Passthrough" settings
Configuring port forwarding on AT&T router models using "Passthrough" settings
I tested it on the NetGear Router. (Unclear if you meant AT&T) The port shows as closed D—restart it.
Do you know if "Cascaded Router" is enabled in your configuration?
It might be possible that AT&T employs carrier-grade NAT on certain parts of its network. This could explain the issue you're facing. I recall hearing about users on AT&T networks being affected by this, but it's unclear whether the company has resolved the problem or if only specific areas use it.
Yah, I'm pretty sure most of their network doesn't but that's a good question for OP. What are the first two sets of numbers being given to your router? IE: x.x.123.456 (Just what's in the first two groups (x's) and not the last two groups.)