Can't host PS3 games or chat sessions online. Please help.

Not sure what topic this really goes under, but since about the middle of September, my PS3 consoles stopped allowing me to play certain games online. Specifically, I can't host game sessions. I can join other player's game sessions, I can sign into the PlayStation Network, browse the internet on the PS3, watch YouTube, etc., but I can't host co-op game sessions. I can't even host chat sessions on the PS3. It's been getting frustrating to have to tell my online friends that I can't invite them and that they have to invite me since I'm having internet problems. Every time I try hosting a game or a chat session, it takes forever to create the session and then comes back with the message "Failed to create session" or an error code/message (8002231D) "Connection to the server timed out" depending on the game. This happens with all of my Resident Evil games that have online co-op, as well as Soul Calibur V.

I have been with AT&T Uverse for several years using a wireless connection to play online games and I've never had an intermittent issue like this before. Again, this just happened abruptly around the middle of last month and it has remained this way ever since. I have a laptop that connects to the WiFi just fine.

One thing I know of is that I visited a friend's home and tested out hosting a co-op session from their ISP (They have Xfinity Comcast) and it worked perfectly!

I don't know what's been causing it, so I performed many troubleshooting steps in hopes of correcting the problem and nothing has worked.

I've contacted Sony PlayStation support about it, and after troubleshooting with them, they resolved that it was my ISP

I attempted troubleshooting with Capcom support which they also resolved was my ISP

I have tried setting up a static IP address or putting it into a DMZ.

I have attempted port forwarding.

I tried making configuration changes to the WiFi in the router via other forum posts

I have tried connecting my PS3 directly to the modem to rule out wireless interference

I have rebooted my modem.

I have even factory reset it.

I have contacted At&T technical support 3 times last month and they couldn't seem to help me. They once transferred me over to ConnecTech who only wanted me to pay them to get this issue resolved.

I tried AT&T support chat again just yesterday and they said they have detected an issue in the line, going on to say that it is related to the network and that they would send out a service technician to fix it. The technician was supposed to arrive between 4PM and 8PM, it is now going on 9:20 PM and no one has been here.

Is it possible that a line issue can simply prevent hosting online co-op sessions? Like I said, I can join other player's games, I can connect to the internet, use the YouTube XL, browse the internet and connect to the PlayStation Network just fine. I just can't host sessions. This is very annoying and I'm getting exhausted troubleshooting this every weekend I have off. It'd just be nice to enjoy my days off being able to play online.

It is my understanding that there's experts on this board that can possibly help with this problem, or can point me in the right direction for troubleshooting so I can contact AT&T support again.

Once more, I have AT&T Uverse, I have a NVG589 Arris Modem/Router, and I have two PS3 consoles that both can't host co-op game sessions online. I don't have TV or phone services through AT&T.