Payment processing error after migrating to a new server
Seems your new hosting environment doesn't have SoapClient enabled in their PHP.

Check phpinfo() output to verify this.

You may be able to enable this yourself or you may need to request it from your new hosting provider - if you have control of your PHP settings you can do this in php.ini, or talk to your provider to have them do it.

See also https://stackoverflow.com/questions/11391442/fatal-error-class-soapclient-not-found