How do I enable the SoapClient class after installing it?

Make sure to restart your server after installing the SoapClient with:

sudo systemctl restart apache2

Had the same issue. Did a yum --enablerepo=ius-archive install php71u-soap. Extension got installed as I saw:

[root@Unixserver modules]# php -m | grep -i soap
soap

Still got the warning in WooCommerce. Even after I restarted Nginx using service nginx restart

Then I /etc/init.d/php-fpm restart and that did the trick

So I was looking for a solution to this problem

SoapClient: Your server does not have the SoapClient class enabled - some gateway plugins which use SOAP may not work as expected.

I did all the suggestions didn’t work:

Edit the main PHP configuration file /etc/php.ini and enable the SOAP extension by uncommenting the line:
extension=/usr/lib/php/modules/soap.so
I even uncommented every line with soap in it

Restarted Php-FPM and Ngnix several times

Did apt-get install php-soap which gave me an error that it couldn't fetch the file.
Failed to fetch http://security.ubuntu.com/ubuntu/pool/universe/p/php7.2/php7.2-soap_7.2.24-0ubuntu0.18.04.1_amd64.deb 404 Not Found

Couldn’t figure out what was the issue. Then I spotted this in the terminal

Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

So the solution was:

Simply run apt-get update and apt-get upgrade on your VPS machine

After that apt-get install php-soap

Restart your Nginx and Php-fpm

Check Woocommerce Status. Happy days!