Orbi RB50 remote management trouble

[Tnrchrds]

I just changed from Cable internet to Fiber Optic.  Most of my devices are working but the Remote Management app says “Internet Offline”

the speedtest on the app says it is connected because I am getting  375mbs. 

One device (Fire TV Cube) will connect to the Orbi but it says there is no internet connection.

i have restarted the Orbi and the Fire TV several times with the same result.  All other devices are working fine.  Sounds like a Fire TV problem but why would the Orbi say it is Offline from the Internet when it isn’t. 

[FURRYe38]

What was the prior ISP modem Mfr and model#?

What is the new ISP modem/ONT Mfr and model#?

You may need to factory reset the router and set up from scratch with the new ISP modem/ONT.

[Tnrchrds]

Old modem. Ubee model DDW366

new modem. Arris model bgw210

[FURRYe38]

Modem Combo Units:
Couple of options,
1. Configure the modem for transparent bridge mode. Then use the Orbi router in router mode.
2. If you can't bridge the modem, disable ALL wifi radios on the modem, configure the modems DMZ for the IP address the Orbi router gets from the modem. Then you can use the Orbi router in Router mode.
3. Or disable all wifi radios on the modem and connect the Orbi router to the modem, LAN to LAN and configure AP mode on the Orbi router.

[Tnrchrds]

That sounds great, but I have no idea how to do those things.  The AT&T installer said he disabled the Wi-fi on the modem since I had the Orbi router.  

[FURRYe38]

Ok, I would factory reset the router and have a wired PC connected to the router and walk thru the set up wizard in a browser...

[JEBBIE]

FireTB will connect and state “Connected with problems”. Shows up in Orbi device list. Rebooted router, modem and satellites as well as did a factory reset on FireTV. Security settings on Orbi set to both WPA and WPA2. Other Amazon devices like show work Ok