Symptoms
After applying an update, one or more features of the WHMCS software may cease functioning, encounter an error, appear poorly formatted, or not appear at-all.
These features could be located in the client area, shopping cart or administration area.
Cause
In the majority of cases, this behavior is caused by outdated customized template files.
The appearance of the WHMCS software can be customized via template files. If a custom template has been created in the past, it must be updated for use with the latest version.
Solution
The template changes between software versions are itemized in the Release Notes. The template changes for 8.2 to 8.3 are linked below:
https://docs.whmcs.com/Version_8.3.0_Release_Notes#Template
Review all the files listed in the comparison view against your custom template files (located at /templates/*your template name*/)
The lines highlighted in red should be removed and the lines highlighted in green should be added:
If the custom template in use was purchased from a third-party vendor, check the corresponding WHMCS Marketplace listing to see if an update is available, then contact the vendor to obtain it.
Once all the template updates have been applied, follow these steps to clear the template cache:
1. Login to your WHMCS Admin area
2. Navigate to Utilities > System > System Cleanup
3. Click the button marked Go next in the Empty Template Cache section.
The template updates are now completed. These steps will resolve the majority of post-update problems.
