The reasons and solutions are as follows

The network operator has restrictions and does not allow multiple devices to be online or multiple devices to share the Internet.

Solution: First confirm whether the broadband account password is entered incorrectly. If correct, you can connect a computer that can dial up to the Internet normally to the management router, use the Mac address cloning function in the advanced settings of the routing optimization master, select clone to the current computer MAC address, save the settings and restart the router.