Paid webinar registration requires Shipping Address

We offer paid webinars to a community of seniors. Payment is via PayPal integration, but most of our community do NOT have a PayPal account. They pay as guests, using a credit card.

Suddenly, operation of the registration page has changed, and not in a good way.

When a registrant presses the "Checkout" button, the page jumps to the top, and nothing seems to happen. In fact, something HAS happened, but it's only visible if you scroll further down in the page. When you do that, you see that you're being asked to enter a "Shipping Address". This never happened before, and it's causing confusion and consternation among our customers.

Has anyone else encountered this? Does anyone understand it?