It is recommended that you refer to the following methods;
1. Enter the settings, search for setting item "Private DNS", see if you set a private DNS, if you have settings, you can taste it
try;
2. Some public WiFi needs to pass the browser certification to connect to the Internet. You can open the browser to access any website to see if you enter the certification page;
3. If the device is far from the router, although the WiFi signal is displayed, it may not be able to connect to the Internet. Please adjust the distance between the device and the router before try.