It's the firewall setting that does tend to block things like this. Yes you claim it's not a firewall so why not put this into the DMZ entry? And drop the router firewall.
There may be old gear that is not ready or won't connect to routers with the WPA+WPA2 mixed mode. Fix? use one or the other, whichever works. And of course try unsecured wifi to work out what this device doesn't like.
My Linksys router failed, so I purchase a new one WRT1200AC. I successfully set up the network and connected my iphones, ipads, Smart TVs, desktop computer, and Xboxes. I also added an external wireless device that connects me to the pool controls and allows me to use the IAqualink App on my IOS devices to control everything. The device shows up on my router page but will not connect to the internet. I successfully connected to my neighbor's network so it's not the range or the hardware. Since it is a router setting issue, does anyone know what might be stopping the connection? I have pinged it and it works. Also, not a firewall issue. Linksys, IAqualink, and Supportrix have tried to help, but failed. To set it up, you open up the panel to the antennae for the device and toggle the switch between wired and wireless. Then from an Iphone or ipad, you search for the Iaqualink network. Once selected, it takes you to the IAqualink setup web page. There you simply select the home network and enter in the password (case sensitive). In less than a minute, the device went online on my neighbor's network, but it has failed to connect to the web on my network about a hundred billion times. Help.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic