If you can still reach IPs (e.g. ping 1.1.1.1) but connection to internet with domain name doesn't work (e.g. ping one.one.one.one) the problem mostlikely comes from DNS configuration.

Have a look to /etc/resolv.conf, it should contains nameserver <ip> for instance : nameserver 1.1.1.1

You may also have a look to the firewall configuration if there is one active.

If you can still reach IPs (e.g. ping 1.1.1.1) but connection to internet with domain name doesn't work (e.g. ping one.one.one.one) the problem mostlikely comes from DNS configuration.

Have a look to /etc/resolv.conf, it should contains nameserver <ip> for instance : nameserver 1.1.1.1

If the ip address is a local ip 192.168.*.*, there is a high chance that the router/server configured is not configured to be a DNS. Nevertheless you can keep it and add after nameserver 1.1.1.1 for clouflare or nameserver 8.8.8.8 for google. So if the first fails, the second should work.

You may also have a look to the firewall configuration if there is one active. The firewall could be configured to block DNS requests (port 53)