ipv4 suddenly not working, ipv6 still works - SHARING HOW I FIXED IT!

I have a Motorola MG7550 modem/router combo that's been working great for about a year. Then suddenly we stopped being able to connect to the internet. The modem/router lights were all on and solid; our phones and TV couldn't connect at all but our laptops could access select websites (Google, YouTube). This helped us realize that ipv6 was connected but ipv4 was not. After hours (and hours) of Xfinity support, Motorola support, and general internet sleuthing, nothing worked UNTIL this morning I tried something dumb and it worked. On my laptop I went to Control Panel < Network and Internet < Network and Sharing Center < click on Connections: Wi-Fi < Properties (at the bottom, not "Wireless Properties"). Then I unchecked the box next to Internet Protocol Version 4 (TCP/IPv4) and hit OK. Then I clicked on Properties again and rechecked the box (then OK < Close). My IPv4 Connectivity went from No Internet Access to No Network Access to Internet. And voila, that fixed our Wi-Fi on ALL our devices.

Now full disclosure, I tried lots of other things first and I suspect this alone wouldn't have fixed the issue but I can't be sure. If I had to guess, I think it might have worked if I either unplugged the modem/router and then did this or if I had Xfinity reset the connection and then did this. It's possible that I needed to do the hard reset to factory settings before unchecking/checking the box. What I do know is that none of these things worked by themselves. I also know that changing the IP address and/or DNS server address was NOT needed as I changed these back to automatic a couple resets ago.

Ok, that's it, I really hope this helps someone :)