WHMCS runs on PHP code and requires several PHP extensions in order to function normally. If there is a problem with PHP on your server, you will experience problems in many areas of WHMCS.
You may experience problems while configuring products for sale, during the purchase process, or when managing individual clients' purchased services.
Some provisioning and server-related issues are due to misconfiguration in your WHMCS installation, while others may be due to networking issues or other server-side problems.
You will see SSL-related errors if the SSL certificate for your WHMCS installation is missing, misconfigured, or out-of-date, or if there are connection issues.
Problems with your system email can prevent you from sending email to clients or connecting to your mail provider.
Issues in the Client Area or your online store can hurt customers' ability to purchase your products or access their purchased services.
WHMCS uses a MySQL® database to store all of your business data, including client and financial records.