No internet with Apple devices, but connected to working router

I'm having a very strange issue with a cable modem/wireless router. It is a Ubee DVW326B.

The cable company came to install it yesterday and was here a while trying to figure out what was going on. The technician was immediately able to connect to the modem/router with his Android phone.

When I tried to connect with two different MacBook Pros, and an iPhone 6 Plus, though, I could connect to the router but got no internet. I could pull up the router admin page and this was/is very quick, so that connection seems fine.

A couple of times (twice) I got a slow trickle of the beginning of a page load, but no complete page load, out of many tries. It was very strange.

Further complicating this was we connected a Sony TV (with android OS) and it connected to the router but could not get internet either.

We swapped out the modem, and had the exact same problem. Both were brand new. They continued to change settings on the office end, but all we got was the same results.

They finally left and said a ticket had to be sent over to Atlanta; they could not figure it out.

Afterwards I thought to check the modem diagnostics and there is an area where the modem can ping or trace route an outside address. It is able to hit Google.com with no problem.

I tried resetting the modem and doing a factory reset. This made no difference.

Has anyone ever heard of such a problem? The only things I can think of is that the Android phone was the first device to connect, and possibly it was older; otherwise it seemed like Android vs Apple, except that the TV, which is brand new, is not Apple (android tv).

The technician's android phone getting a 50mb signal on speedtest is the really confusing thing. He even turned off his cellular signal to confirm he was connected to the modem.