FIX FOR received new xfinity gateway, microsoft surface pro 3 no longer can connect to wifi

I recently had this frustrating issue and am posting the fix to hopefully help others who had the same problem...

Recently we have been having network issues, slowness, etc., and xfinity determined our gateway was outdated, and sent a new one free. We set it up and activated it per their instructions and all our devices seem to work with it and the connections are much faster, EXCEPT this old Surface Pro 3 running Windows 10 Pro. When trying to connect to wifi, the Windows connection manager just said it can't connect, with no other info. We have kept the PC up to date with Windows updates and nothing changed other than the gateway (kept all passwords and SSIDs the same, etc.) Tried calling Xfinity support and they checked everything and couldn't get it to work, they just said some older devices aren't compatible with their new modems (wouldn't say what specifically) and to contact the PC manufacturer (yeah right, this laptop's been out of warranty for 6 or 7 years at least). I tried all the network troubleshooting, uninstalling & reinstalling the driver, network reset, etc., nothing. Well, after much googling, I found the answer is that apparently the new gateways use the newer WPA3 security and you need to update the driver for the Marvell network adapter. In device manager, telling it to update driver it said the latest driver was already installed - not true! First I had to get the laptop onto the Internet - I tried using my smartphone's hotspot but got the same error as with the xfinity wifi. However, there's a "maximize compatibility" setting in my phone's hotspot setting, and with that selected, the laptop could get online. Go to 

https://catalog.update.microsoft.com/Search.aspx?q=marvell+avastar+ac

and download the first item. Double click it and copy the contents to a folder on your PC. Then open Device Manager and under Network Adapters, double click the Marvell wireless adapter, and click the Driver tab. Click the Update Driver button and click the "Browse my computer" option, and select the folder you copied the drivers to. Install those and reboot when it prompts you, and voila! Fixed!

Here is the video I found that walks you through how to do all that:

https://m.youtube.com/watch?v=aBrTgPrE4X4

It would have been nice if Xfinity knew about this but I understand they can't support all the 1000s of devices out there, so I just wanted to share this to help someone with a similar problem. 

Good Luck!