(DNS must be filled in for DHCP service settings in the router)

B. If the above methods fail, manually assign static IP in the router settings, fill in the IP assigned by the router in the mobile phone, and finally restart the router.

(Note that DNS is mandatory)

C. If you can't log in, it's probably in the phone settings, so you need to check the settings yourself. Be careful not to use proxy connection.

(Some mobile phones automatically choose proxy connection, which leads to connection but not Internet access, so the proxy connection is turned off. )

PS:

When the mobile phone is disconnected immediately after connection, or the Internet can be connected after a period of time, the static IP of the router and the mobile phone must be set manually to solve the problem, instead of automatically obtaining the IP.