I upgraded WordPress/WP Invoice and now 'PayFast' no longer appears as a payment option.

I upgraded WordPress/WP Invoice and now 'PayFast' no longer appears as a payment option.

When upgrading either WordPress or WP Invoice, the PayFast payment module files may be deleted.

You simply need to reinstall the module following the installation procedures and the 'PayFast' option will reappear with your previous setting intact.