No visible button for Free Subscription Payment Gateway on Registration page.

Hello,
I'm having an issue with the Free subscriptions gateway (that's my guess).

I'm testing the subscription model for a customer. We have three subscription plans, a basic (free), a premium and a gold.

So far I setup one unique payment gateway, the "Free subscriptions gateway" option.

When I try to register a new user, after I click on the button for the desired subscription plan, I land on a following page with a statement in green "Please check the details of your subscription below and click on the relevant button to complete the subscription.".

The coupon field is visible, as well as its button "Apply Coupon".

But no button to pay for the subscription is present or visible. So there is no way to initiate the payment. The page does not bring anywhere. It's a dead end.

Nevertheless, the username is registered and the customer is left unsure about the outcome of the registration process.

In fact, if the customer would like to start over again, the website says that that particular username is already registered.

May I have your support in this?
Best,
Carlo