Hi @smiranda,
The “Custom text shown on block pages” option on Wordfence > All Options > Brute Force Protection > Additional Options is designed to add some explainer text on the Wordfence-branded 503 error pages that are shown to people locked out from your site entirely after violating the rules you have set there.
I feel like this may be more related to error text shown inline for your login pages, or perhaps the login process entirely? Firstly, I would test whether brute force blocking is working for the default WooCommerce login page URL at yoursite.com/my-account/
After this, test the brute force blocking with the login modal pop-up found on the top-right of your homepage instead. If it works on the default WooCommerce login page, but not the modal then we could be looking at issues with the way that integrates with Wordfence or whether there could be a plugin conflict breaking it.
Thanks,
Peter.