Why this Post method returns a 405 error?

I am receiving a 405 Error when i try to use the post method from a booking engine for our small hotel website.
Here is the code that the booking engine provider asked us to integrate below and the temporary url of website with the booking engine in questions on home page.
https://nicolass-trendy-site-521bc7.webflow.io/
What are we doing wrong?
We used this HTML block for it.

<section id="hbe-bws-wrapper-widget-code"></section>
<link type="text/css" rel="stylesheet" href="//book.securebookings.net/css/search-wdg.css" />
<script type="text/javascript" src="//book.securebookings.net/js/widget.search.js"></script>
<script> 
jQuery(document).ready(function() {
             $widget("#hbe-bws-wrapper-widget-code").searchWidgetCode({
            id: "cdc12a82-35c5-1668031886-4530-b288-fdfc406a9e3e",
            lang: "en",
            Layout: 0,
            ShowPromoCode: 1,
            ShowFilterSearch: 1,
            ShowBestRate: 0,
            InsiteUrl: "https://nicolass-trendy-site-521bc7.webflow.io/reservation",
            ButtonName: "Check Availability",
            ButtonBackground: "#4391DA",
            ButtonText: "#FFFFFF",
            WidgetBackground: "#AA8453",
            urlS3Json:"new-hls"

            });
            });
</script>