error – sudo: effective uid is not 0, is sudo installed setuid root?

Check the permission and ownership for sudo :

[root@baselinux ~]# which sudo
/usr/bin/sudo

[root@baselinux ~]# ls -ld /usr/bin/sudo
—s–x–x. 1 root root 123832 Jun 7 2017 /usr/bin/sudo

if not own by root:

chown root:root /usr/bin/sudo

then

chmod u+s /usr/bin/sudo