Check if you can reach a remote server
dig a gmail.com
If this timeouts then try over one of dns resolver directly
[~]# dig @8.8.8.8 a gmail.com
; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.el7_9.2 <<>> @8.8.8.8 a gmail.com
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached
Timeout means DNS resolver is dead
[~]# cat /etc/resolv.conf
nameserver 208.67.222.222
nameserver 8.8.8.8
nameserver 1.1.1.1
Try to find working resolver
dig @8.8.8.8 a gmail.com dig @1.1.1.1 a gmail.com dig @208.67.222.222 a gmail.com
And comment out which don’t work in /etc/resolv.conf file
If none of your open dns are working try to use resolvers which provides your ISP/Datacenter.