Please do the following steps to be able to log in through the App and watch the channels:
Open the AT&T router App on your phone >> Then disable the Security Amrmor.
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Additional Information that may help you for some AT&T Internet router App versions:
Please download AT&T Smart Home App or AT&T ActiveArmor Mobile Security App on your phone/App Store or you can access it directly to your web router login. The login details are available on the back of the router sticker.
AT&T ActiveArmor Mobile Security App >> Security >> Firewall will need to be switched off the security in the AT&T smart home app (See the below screenshots):
Also, check this YouTube video for more info: AT&T ActiveArmor Mobile Security App | Advanced Security Overview | AT&T - YouTube
In other AT&T App versions, Please Select >> Active Armor Alerts >> Turn OFF, see the below screenshot:
Follow the steps below if you want to log in to your Router web, the router web login details are available on the back of the router device.
Watch this YouTube video: How to configure the AT&T BG210 to enable IP Passthrough features in 5 minutes! - YouTube
1- Make sure to select the Firewall >> Packet Filter >> Press on Disable tap like the screenshot below:
2- Go to Firewall Advance >> Make all options OFF (Disabled) like the screenshot below:
3- Restart your Router Device >> Restart Device like the screenshot below: