Have you setup Wishlist Member WooCommerce Plus on an external membership site (this can be done using The External Membership Sites Add-Ons Bundle) , but getting a message that the Authentication is “Not OK” (see screenshot below)?
This is why and how you can solve it:
If you are getting this message it means that the membership site’s homepage is not a WordPress based page, it is probably a HTML code.
In order for the plugin to authenticate the products, it needs to send information to the membership site.
And because the homepage is a regular HTML page, the information is not processed correctly, causing the authentication to fail.