Help purchased Osclass plugin Pay Payment Plugin
but I do not know where to put the following code exactly <? php if (function_exists ('osp_product_to_cart_link')) {echo osp_product_to_cart_link (); }?

@Fabio
Simply use hooks so you do not need to modify theme files.
Note that product should be allowed for sale, should have sufficient quantity and owner of listing should be set as seller in eCommerce settings, otherwise add to cart button will not be shown.

I thought this was also included in the plugin purchased https://osclasspoint.com/osclass-plugins/advertisement-and-monetize/banner-ads-plugin_i56

@Fabio
https://osclasspoint.com/osclass-plugins/payments-and-shopping/osclass-pay-payment-plugin_i46
This feature require Banner Ads Plugin to be installed. It is paid plugin.

sorry because on my profile there is no purchase of Osclass Pay Payment Plugin

What profile?

Fabio Massaro [email protected]
 Receipt No.: 4158-6562-5596-2244

@Fabio
You still did not explained what is problem.
Your order is completed and successful.

On my MB theme account when I go to Order history and details
I can not find the purchase of Osclass Pay Payment Plugin on ORDER HISTORY

@Fabio
You bought it on osclasspoint.com, why you login to mb-themes?