I was having issue with the internet for few days on my windows 10 lenovo laptop and I followed so many suggestions and even reset the laptop but nothing worked until I found this.
The trick was to open CMD window as an administrator and run these commands and restart your computer.
c:\netsh winsock reset catalog c:\netsh int ip reset reset.log c:\ipconfig /release c:\ipconfig /renew c:\ipconfig /flushdns
That fixed the issue where my computer was connected to wifi but had a yellow triangle saying either limited connection or no internet connection. When I used windows troubleshooter it was complaining about "the default gateway is not available - not fixed"
There was no issue if I use the hotspot from mobile (iPhone) though but it's too expensive to continue using it.
Finally the solution above solved my laptop's internet issue.
Above solution didn't work after next day. As wifi connection is OK, I can go to modem setup page. Here go to "Channel and SSID" and under Bandwidth select different MHz option than it's currently selected. So, I switch between 20MHz and 20/40MHz whichever works.