C7000 Nighthawk will not allow Nest Doorbell to connect. NC009 error.

[raylo2020]

Netgear C7000 Nighthawk modem/router Will Not Allow Nest Hello Doorbell Camera to Connect.
It currently has Firmware Version V1.0.1.33.
Doorbell was working and connected for one year, 1 month, but when I migrated my nest account to the Google gmail I lost my two nest device. I added the Nest video doorbell and now it wont let me connect. Im getting the error code NC009 (15.5) which means:
"These error codes mean your internet firewall may be preventing the Nest app from adding Nest Cam to your network. Or, there may be some other issue with your network". Here are the steps I have done so far and it still not working:
1. Used 2.4ghz and 5ghz to connect the next hello and none of them worked and tried both on my Android mobile device and didnt work.
2. Used another phone which is IOS and that didnt work and got the same error.
3. Used another phone to connect to my hotspot on my phone and connect to doorbell and still getting the same devices.
4. I have tried enabling/disabling UPnP and it still didnt work.
5. I got a new Nest Doorbell and the new one is saying the same thing.
If anyone had similar issues and got it to work please share or if you have any ideas on my next step to get this solved. Im not sure what to do next.

[plemans]

so it worked fine before the account migration?

And you can setup a phone in hotspot mode and it still doesn't work? 

If that's the case, I wouldn't be looking at the modem/router, i'd be looking at the account migration and be contacting google. 

Reason why I say that is:

1. you've ruled out it being a device issue by getting a different Nest doorbell.

2. You've ruled out it being a router issue because

    A. it worked fine prior to account migration.

    B. It still doesn't work if you hotspot a phone to try to set it up. 

3. Its the only devices with issues (from what you've written).

Have you contacted google support? 

[raylo2020]

I have contacted Google and they said it was fine on their end. I signed back onto my old account that was before the migration acct and my thermostat was there but not the nest door bell. Tried to install the nest doorbell and still the same code of firewall is too high. Tried hotspot and still not working. Is there another way to lower the firewall.

[plemans]

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@raylo2020 wrote:
I have contacted Google and they said it was fine on their end. I signed back onto my old account that was before the migration acct and my thermostat was there but not the nest door bell. Tried to install the nest doorbell and still the same code of firewall is too high. Tried hotspot and still not working. Is there another way to lower the firewall.

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I wouldn't. And I don't think that's the problem because it doesn't work when you hot spot your phone. do you have a different router you could try or a friends place you could try seeing if it'd do the setup?