if ping cloudflare.com doesn't work
but ping 220.127.116.11 does work
then you might have a DNS problem.
If you click on the network icon (network-applet)
and choose 'Connection Information'
you can check if a DNS address is present.
if not, check your network settings:
click on the network icon (network-applet)
and choose 'Edit Connections'
then select your current connection
Click the tab 'IPv4 Settings' and 'IPv6 Settings'
'Method' should normally be 'Automatic (DHCP)' for IPv4 and 'Automatic' for IPv6
Eventually, the problem could be somewhere else on your homenetwork or router or even in the connection to your ISP.
If you use VPN, make sure that you also get the DNS-address via vpn.
You might have to enter the DNS manually but all that should be found
in the info you received from your VPN-provider.