“Place the order button” do not appear

Hello Guys,
I bought your plugin:
WooCommerce Cart All in One – One click Checkout – Sticky|Side Cart
Regular License
6 months support (expires on 25 Oct 2021)

I have a big issue: the “place order button” in the last step in some cases disappears.
I am working in mobile e-commerce using woo-commerce, dokan, and some plugins as yours. I have seen that in most of the cases when I try to complete an order, the “place order button” does not appear on the checkout.

Checking on my chrome developer tab I have seen two different returns from this script:
https://chic.menu/menu/wp-content/plugins/woocommerce-cart-all-in-one/assets/js/sc-checkout.min.js?ver=1.0.1.5

If it returns 1 the button is regularly showed
see:https://chic.menu/2.png

if it returns 0 the button is not showing
see:https://chic.menu/1.png

Practically 90% of the cases return 0, so it is not possible to complete the order.

Could you help me to fix this issue?

And, do you have a trick for the footer selling gallery?
My project is a multivendor one, so how I can list products only from the relative vendor? I have seen the script suggest products from other vendors inside the website.

Thanks a lot for your help and plugin.
Giadina