Anybody able to register without code (plugin stopped working)

Hello,
I have been an user of this plugin for 2 years and it has always been working flawlessly, with hundreds generated codes.
Until, I think, a couple of weeks ago, maybe for the new WordPress update.

Now the Invitation codes text field is completely bypassed.
any user can register just by entering any fake code or leaving it blank.
This obviusly defeats the entire purpose of this plugin.

I noticed that I am also unable to edit the text label displayed under the text field.
Even if I edit the label in the backend, in the frontend it will remain the old one (while the backend correctly works and saves the new label).
Also if I choose to uncheck the label option, label will remain there in the frontend.

It is like if the plugin is completely bypassed, and its settings ignored, but I have a dummy text field in the registration form.
Even if I uninstall the plugin, the text field and label stay in their place.

I tried to disable my caching plugin, but same issue.
The Woocommerce version has remain unchanged (registration page is the WooCommerce one).

I will happily make a donation if able to fix my problem.

Thanks.

The page I need help with: [log in to see the link]