CentOS 7 updated repo after its EOL

mirrorlist.centos.org doesn’t exists anymore. So, your default repor wwith yum doesn’t work. Try using the following processes, it worked for me, hope this works for others as well.

sed -i s/mirror.centos.org/vault.centos.org/g /etc/yum.repos.d/*.repo
sed -i s/^#.*baseurl=http/baseurl=http/g /etc/yum.repos.d/*.repo
sed -i s/^mirrorlist=http/#mirrorlist=http/g /etc/yum.repos.d/*.repo

Ref:
https://serverfault.com/questions/1161816/mirrorlist-centos-org-no-longer-resolve