Deco M9 Plus (AC2200) satellites blinking red in AP mode
I have been using this system for a couple of years without issue. I recently switched the Deco to AP mode. All Deco units are hardwired to an Arris BGW210-700 router provided by AT&T (fiber internet). The main unit is shows green. The other two units blink red. I have restarted the router, the main unit, and the satellite unit multiple times. The internet connection through all units is good. The Deco app shows all units connected.
I have seen similar posts but have no seen a resolution. My problems seems most closely related to
1. Deco works in access point mode with LED in red but the internet service is working well.
The internet online detection DNS requests have been blocked by the firewall of the main ISP router so only the LED is red but the internet connection is fine.
What is the resolution for this? Do I need to configure something in the Arris router?
Any help would be greatly appreciated.