If yourdomain.com/cpanel and yourdomain.com/whm both go to a 500 internal error page instead of redirecting to the control panel login, it is most likely due to a missing file in the CageFS skeleton.
First, edit:
/etc/cagefs/conf.d/perl.cfg
by adding the following code to the paths
/usr/bin/perl-bin
Then run the following command
/usr/sbin/cagefsctl --update
If you still have questions, feel free to contact us by opening a support ticket or by using our live chat feature.