Router keeps giving me "Router Password Reset" page

[mc510]

I recently installed the latest Netgear firmware on my R7000 and then used the GUI to restore factory settings. I've set a new password and am using the router, but every time I try to log into the GUI it keeps giving me this after I submit my user/password combo:

Router Password Reset

Your Device is disabled, Please try again in 1 minute. We can help you reset your router's admin password. You need your router's serial number, which can be found on the router label. Enter your router's serial number in the field and click the Continue button.

Enter the router's Serial Number

(You can find it on the router product label.)

If I refresh the browser and then log in again, it usually lets me in. Though at the moment, I'm in the GUI but I can't do anything because each of the pages under Advanced are showing me the same Router Password Reset message. What's going on and how do I get this device to settle down and accept the fact that I have logged in with my true user/password?

[FURRYe38]

What browser are you using? 

Be sure to clear out ALL broswer caches before entering the web page.

Try a different browser, MS Edge, FireFox or Opera. 

If this fails, factory reset the router and thru the set wizard and enter in new information. Be sure to write down all important information for safe keeping.

[mc510]

I'm using Chrome browser, and I'm on a Chromebook so unfortunately don't have the option of using another browser. I've cleared the cache (again) but no improvement. I'm sure I did a NVRAM reset at some point while installing the new firmware, but I don't remember if I did a 30-second-button-push reset after installing it. I think I did, but am not sure, so I'll try again when I can find a time that my family isn't using the internet. 

Question - after full factory-reset, should I be able to log in with "admin/password" or is this a new Netgear thing that you're required to enter the serial number from the bottom of the router?

[FURRYe38]

Only a 10 second press of the reset button then release is needed.

After you factory reset, when you open up the browser and navigate to 192.168.1.1 or routerlogin.com you'll be directed to use the Nighthawk app or if you scroll down to the bottom of the page, you'll see a link that says I don't have this app and select this, this will start the web based setup wizard. Walk thru this.