The router is not open or is in the range of the router signal. If you are too far away from the router, you will not be able to get the router's signal. Make sure that the location is within the range of the router, the WiFi signal can be searched, and the signal is stable.
two
The WiFi network is faulty. Make sure your router is connected and turned on, and that there are no restrictions set on the router server. For example, if the MAC address or IP address filtering permission is set to prevent the mobile phone from connecting to WiFi, you need to modify the router configuration, or contact the router administrator.