DSL line 2 down

Years ago, when I went for 50 MB service on my U-Verse system, I had to get another gateway that supported 2 DSL lines. I replaced that gateway with a Pace 5268AC a couple of years ago for a service issue, and I know then that both DSL lines were connected and working. Yesterday, I had a problem with the system, and when I checked the gateway, DSL line 2 was down. I rebooted the gateway, and line 2 never would connect - but everything is working fine again. I did speedtest on the internet connection and it is showing 48MB connection, just like always. TV system and phone are working fine, and Netflix is streaming with no problems, yet line 2 is still showing disconnected. Line 1 is showing 55439 kbs download speed, which seems faster than what is used to connect at.

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Has U-Verse improved their DSL so that 1 pair will support 50 MB service? Apparently so. Does that mean I could now get 100 MB service? It is not listed as an option - Internet 45 is the highest listed...