Websites - Access denied

Does this happen with more than one browser on the iMac and iPhone?

What Firmware version is currently loaded?
What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too? 
Be sure your using a good quality LAN cable between the modem and router. CAT6A STP is recommended. 

Using ISP DNS or custom DNS? 

Be sure to disable any MAC Address randomizers on phones and pads while at home:
https://community.netgear.com/t5/Orbi-App/NETGEAR-Mobile-Applications-and-Apple-Devices-FAQ/td-p/2220016/jump-to/first-unread-message

Try disabling the following and see:
Armor, IPv6, Traffic Meter.

mweiby wrote:

I installed a new RBE771 with 2 satellites about two weeks ago updated to latest firmware. Yesterday, we could not access eBay.com and received an access denied http://ebay.com message (no "s" after http). It was working OK previously. this happens on iMacs and iPhones. This replaced an older Orbi and there we no issues for years.

 

If wifi is turned off on the iPhone bay can be accessed thru cell data.

 

I powered off the modem and Orbi. It did not fix the issue and now some of my devices won't connect. 

 

Parental Controls is not enabled.

 

I have an 2 year old Xfinity modem that was also connected to the old ORBI.

mweiby wrote:

Yesterday, we could not access eBay.com and received an access denied http://ebay.com (no "s" after http)

this happens even if you enter https://ebay.com?