Correct. ET+ integrates with your eCommerce plugin of choice (most popular by far is WooCommerce). It doesn’t have any cart, checkout, or payment gateway functionality.
A good place to start might be enabling WP_DEBUG and WP_DEBUG_LOG and sharing any debug messages you see while changing tickets quantity, navigating your site’s home page, events page, single-event pages, and any other of your site’s pages relevant to this ticket.
You might also include a screenshot where you’re expecting to see the option you’re looking for.
And maybe try downgrading to the previous version of https://wordpress.org/plugins/woocommerce-gateway-stripe/ (assuming that’s the one you’re using), since the version you’re using was released just 2 days ago.