Windows 11 Broadband Connection Error 720

Error 720 indicates: Dial-Up networking could not negotiate a compatible set of network protocols you specified in Server Type settings. 

Resolution:

Check your network configuration in network control panel and try the connection again.

For detailed fix, and steps, refer this Microsoft support article:

https://support.microsoft.com/en-us/topic/error-message-error-720-no-ppp-control-protocols-configured-aa71f6df-1765-82dd-9f70-eb00f2fe1b86

Let us know if this helps!

Run Command Prompt as an administrator, type `netsh int ip reset` and `netsh winsock reset`, then restart your computer.