We are providing a custom child theme of WHMCS twenty-one theme. Here just has the
footer.tpl files and everything is working from WHMCS twenty-one theme. You can check out our provided files.
We mean to say there is no relation between our child theme to the payment method because the payment method works with WHMCS twenty-one theme.
If you need to update your system please do it to check the issue. or try to use the WHMCS twenty-one theme directly to check the issue.
ThemeLooks Support Team