Invalid Device error everytime I try to log in to home network manager

The best advice I can give is to get a decent modem and router. Check these out

TP-Link 8port switch  
Asus RT-N66U

Motorola SB6141

Let me know if I can help in anyway 

The fact is that when I'm paying them for the modem/router the advice I receive should not be go buy new stuff..... They need to fix the manager so that people can actually access it.

I think they should disable the manager IMHO. The best way to configure a device like that is the web UI. No different then a router, you can access it via 192.168.0.1 with user <admin> and password <password>. See page 8 of this manual 

If that doesn't work, someone must have changed it, probably during install. If no one wrote it down, then you will have to reset the device to factory. I only suggest doing this if you have configured a router before. For instructions see page 43 of manual above. For port forwarding see page 30-31. 

PS. Does Cox allow the remote support of the gateways as per page 35?

I have already tried accessing the router gateway directly using 192.168.0.1  I can access it perfectly fine other than the fact that no matter what browser I use, I have absolutely no add or save buttons, or any other buttons.  Why bother to call in and get walked through something I am already very familiar with, when I've already tried and it doesn't work?  Also, the information about this modem that I have read all states it must be done through the home manager, and not the gateway.  I wish the gateway worked, because I would have been done with this without every getting on the forums.

Here is the portforwarding screen.  As you can see there is no option to scroll the page up or down and there are no apply buttons or any other.  Every page of the gateway is like this.

Odd. I thought you just prefereded the Home Network manager, I didn't know the web UI was actually broken/disabled/ I have never heard of such a thing. Maybe a firmware issue? When I had mine I could configure it. The main issue I had was some of the features were removed because mine was a Beta unit. 

Maybe you have a old unit? Try turning off the style and maybe then you will be able to see the buttons. To remove style CTRL + V > Style > No Style. 

CTRL+V does nothing on any of the pages.  The unit should not be old as it was just installed in November.  This is why I'm to the point of no return.  The UI does not work and neither does the home network manager.  Congrats on a double fail.

Yea, not sure what to tell you. Thats why I think those things are junk. If you want to ditch and you have a better offer, then go for it. If nothing else, if you leave, then come back later, you will have access to better deals. Sadly thats how the system works  Let us know if we can help in anyway. 

wow, the support on here is minimal at best.  For support forums I am giving this a 0.  The equipment doesn't work the way it should and I'm then told leave and come back for better deals?  I haven't even had service for 2 months.  This is the epic fail of customer service.  I can promise that if I leave I WON'T come back and I WILL spread by word of mouth to ALL of my friends and family to avoid Cox Cable like the plague.  This is beyond ridiculous.

OK Bye bye 

Kinda wish I didn't help at all now. BTW, how many people have you helped on this forum? 

how is telling me to leave and come back help?  Last I checked that is just another failure of support.  I'm not asking for anything more than to have equipment that works by the company I pay to provide it.  So I'm sorry if you feel that helping is telling someone to leave and come back for other deals.  I don't feel that is helpful at all.  So if anyone has any real advice on how I can port forward without costing more money by buying different equipment I'd be glad to try it.  Otherwise, quit saying leave and come back because that just says leave we don't care about our customers.

Your not my customer, I am not Cox. You don't pay me anything. I am just a guy who is bored so post on forums to help people. And I did try to help you, but the truth is you got crappy equipment. If the firmware is broken then bring it back and buy something that works for you. I don't see how me being honest and frank is not helpful. Did you want some line of copy/pasta saying how sorry Cox is about your trouble? Or did you want a solution? I was just trying to provide a solution. Take it or leave it, but don't go spitting on someones help just because it wasn't the solution you wanted, and don't complain about not getting help if you are not providing help to others. Good day. :-)