If you're getting an error in Windows 10 that you don't have a valid IP Configuration, don't waste your time calling AT&T or Comcast. It's not them. Windows 10 released an update bug to their operating system this week. I have seemed to figure out how to fix it. If you can't follow what I'm doing, don't try, go ahead and contact me via phone or email and we'll set up a time to fix over the phone. It's reasonably quick and I charge a lot less than my hourly minimum if I don't have to come out. We can do a credit card over the phone.
Open DEVICE MANAGER, either by going to CONTROL PANEL and then DEVICE MANAGER or typing DEVICE MANAGER into CORTANA SEARCH.
Go to NETWORK ADAPTERS. Click on the greater than/less than (not sure which one it is!) next to NETWORK ADAPTERS. This will display a dropdown list of adapters like Wifi, Ethernet, and Bluetooth.
Right click on the appropriate one related to your problem. If you connect with WIFI and now you can't connect with WIFI, right click on WIFI. If you are directly connected via a cable to the internet, choose the ETHERNET adapter. Select UNINSTALL. DO NOT CHECK THE BOX THAT ALLOWS YOU TO OPTIONALLY REMOVE THE DRIVERS. Click OK/Uninstall/Delete (not sure of the actual button name)
When it is done, Reboot the computer by clicking the Windows Icon in the bottom left of your screen and clicking on the power icon and choosing RESTART. Do Not Push the Power Button on the Hardware, that will probably only put it into sleep mode and it won't allow you to finish the repair.
After you reboot, you will need to reconnect to your WIFI network. Once you reconnect, all should be working.