This may be due to multiple reasons. Perform the following steps to troubleshoot:

Step 1: Check the Wi-Fi name and password

If you forget the router's login password or the Wi-Fi password, restore your router to its factory settings, and follow the instructional manual to reset your router. After the factory settings are restored, the existing configurations of the router will be lost. You need to reset the router to access the Internet.

Step 2: Check whether your device and your router use the same encryption mode

The encryption modes of the router include no encryption, WPA2 PSK mode, and WPA/WPA2 PSK hybrid mode. If your device does not support your router's encryption type, the device can't connect to your router's Wi-Fi. It is recommended that you set your router's encryption type to WPA/WPA2 PSK hybrid and try to connect to the Wi-Fi again.

Step 3: Check whether your device (phone/computer) is on the blocklist/trustlist of your router

Your router supports the Wi-Fi blocklist/trustlist, which controls access to the Internet. If your device has been blocklisted by the administrator, you will not be able to access the Internet. If the administrator set up a trustlist, but your device is not on the list, you won't be able to access the Internet either.