I use WooPayments and the express checkout buttons – google pay and apple pay – didn’t appear on the Checkout page although they are shown and can be used for payment on the Cart page. The setting for this method are checked (where to show) and the buttons appear on a page with the woocommerce default shortcode [woocommerce_checkout] (albeit on top). The issue is also present if Stripe method is enabled.
No other plugins seems to interfere here.