Only a couple of customers showing up

Hello. This seems like a great plugin, as this feature should really be built into WooCommerce, but it is not working for me. The Loyal Customers panel is showing only 2 customers (out of 80+ registered customers).

I am using an out of date version of WordPress. Could this be the only reason?

Thanks,
Chris

https://www.ads-software.com/plugins/woocommerce-loyal-customer/