Without exaggeration for years I have fought this beast "No Internet connection" I have had broadband engineers, new hardware, software so called fixes to no avail and then for Christmas I upgraded my Roku and yep there it was. I came to the Roku support page and dozens of you screaming at Roku for a solution but I had the problem without the new Roku, so I again searched the Internet, and found the answer, for me!
https://lazyadmin.nl/home-network/wifi-connected-but-no-internet-fix-it-in-5-min/ is the link to where I found the answer, and the author deserves a Gold Medal, I have bookmarked his page as it has a lot of sensible advice without technical gobbledy-**bleep**
The simple solution if to press Win key + “R” key
Enter cmd, and then ipconfig/flushdns and magic instant resolution of a problem I have had for years. I hope some of you frustrated people will give it a go as it is no major change and can't do any harm IMO