Is there no longer a channel 9900?

It's still there.  Check that it didn't accidentally get hidden.

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Channel is still listed. I get error code:0 failed to load resource.

Sorry. Didn't mean to dbl post. Having trouble signing in.

Try rebooting the DVR if you are having issues loading the app.

No luck. Thanks, though.

Spent almost an hour on the phone today with at&t. Finally, a senior technical rep, going though all the notices she's received in the last week, found one that stated that this channel was retired on August 27, 2021. My spouse used the Call History app almost every day to call people back or check who called but diid not leave a message.

Way to go u-verse! Now the only interactive app left which I might use on the TV  is the weather app. Everything else I've ever found useful in the interactive menu over the years is gone.
Of course, the instructions on how to get to channel 9900 are still on the at&t web site, and the instructions on how to get to the call history in a web browser are also wrong.

My channel 9900 came back a couple of days before they pulled the plug. I used it everyday also and am really disappointed.