I have a Roku streaming stick that works fine and plays any channel without buffering, however when I go to system, check connection it states "not connected to internet". Using my phone and the speedtest app and fast.com, with phone placed next to the device, I am getting 380Mbps. I have 2 gigabit internet and a wifi mesh system that handles the incoming speed excellent throughout the house. On 2 other Roku devices in different rooms, I am getting 200+ Mbps on check connection. As I said, the device in question works fine and when I moved it closer to the main router, I still got "not connected to internet" but I can stream whatever I want on any streaming channel. I have reset the internet connection several times and checked for any unusual setting in the "secret menu". The only thing I haven't tried was a complete factory reset and if that's the only option, I'll throw the thing away and buy another. Any thoughts?
My first thought is if it "works fine", why are you bothering to check the connection? That "Not connected to the Internet" message isn't very accurate, as you've seen. From what I can tell, it's unable to reach some Roku site that obviously isn't important for streaming. Content blockers are sometimes to blame. If everything's working, just ignore it.
When you select "Check Connection" you disconnect from your AP then reconnect to the AP, then establish a new LAN connection, then a new internet connection. E.g., I usually see mine change to a different channel on the AP. The LAN IP address never changes because I have a DHCP reservation for each device. Yours may get a new address. Whatever, it's not telling you that you didn't have an internet connection at the time you were streaming just fine. It's telling you that it checked for an internet connection and failed between the time you dumped the connection (by selecting "Check Connection") and successfully established a new connection. A lot of things might cause this but it means nothing if it returns a channel number, an IP address, and a speed result.
If it returns none of these, you may send it to me for recycling.