If your website is down due to one of the following error it means you haven’t apply the CURL fix;
PHP Warning: PHP Startup: Unable to load dynamic library '/opt/cpanel/ea-php70/root/usr/lib64/php/modules/curl.so' - libnghttp2.so.14: cannot open shared object file: No such file or directory in Unknown on line 0
or
CURL is not installed or is disabled on your server and it is required for WHMCS to run
Here is a fix to the problem and it is really simply to be applied;
CloudLinux 6
yum update ea-libcurl
CloudLinux 7
yum update libnghttp2-devel
My WHMCS website were down for almost 2 days because of this bug. I had to downgrade my PHP to 5.6 for a temporary solution before CloudLinux actually released a fix. I hope everyone else are not having the same problem as I did.
Soure: CloudLinux Blog