Question Wifi connected but 'no internet'

[Nk-]

Hi all, so I'm using an oppo a91 phone, android 11.
I keep randomly losing my internet connection when on the wifi. It doesn't lose the connection as if I was too far away, it stays connected but with with a subtitle that just says 'no internet'. It doesn't even switch to mobile data. And all I need to do is just disconnect and reconnect the wifi on the phone, and it works again. But it keeps reoccurring. I tried resetting the phone to factory settings and even brought it back to the shop for repair, where they say they changed the phone's mother board. No change. Is there another hardware problem that can be causing this? Or is this something else? Basically looking to know if it's worth bringing it back for repair again if they already changed the mother board, or if it's a waste if time.
No problem when using mobile data on that phone instead of wifi, no problem with other devices on the same wifi network.
Any help is appreciated

 

[Nk-]

I understand you're having difficulties accessing the internet, but you're connected to Wi-Fi. I really hate to be that guy, but have you tried unplugging the power from the modem and router, waiting 30 seconds to one minute, and plugging them back in? If so, and that didn't resolve your issue, It appears that your Local Area Network or LAN is functioning properly, while your Wide Area Network (WAN), i.e. the connection between your personal Wi-Fi network, and the internet isn't functioning properly, at which point it is best to contact your Internet Service Provider or ISP for further troubleshooting. Hope that helps! If you have any additional questions, please don't hesitate to ask.

I’m assuming windows 10?
Start button > Type Network Reset
Reset it
Restart
Profit
This does many things at once including resetting services and replacing drivers

Thanks.
So the issue is on one android smartphone only. No problem with other devices so I guess I can assume the problem is with that particular device -hardware or settings..- and not with the network itself. And a quick disconnect/reconnect of the wifi,on the phone, always works, but it keeps reoccurring randomly. What I'm wondering is if it can still be some hardware problem considering they changed the motherboard and it didn't solve it. I have no clue what hardware part controls this. And if not then what can it be?

 

[Mr. Underwood]

In settings, run update Android system. There are a few updates
available. Then update it again and a few more come. I updated and
a Wi-Fi phone appeared to be available. Then it automatically connected to my home router Wi-Fi instead of what ever Wi-Fi your carrier has out there. ( If you have a router with Wi-Fi, at all) Upgrade with your Internet Provider and get one with Wi-Fi.

Some days I get bad reception and keep my smartphone near the window. Sunny days I get good reception, but maybe not overcast days.

What kind of Internet is available through the cellular network? I have Wi-Fi (off) and Bluetooth (off) and I still have a good connection.
The problem I have is not NO INTERNET, but I wonder why I have
internet.