The booking widget isn't appearing

Check these in order

• You can see the code itself on the page. It went into a text block rather than a code block. WordPress wants a Custom HTML block, Squarespace a Code block, Wix Embed a widget.
• Nothing at all, not even a gap. Your site may have stripped the <script> tag on save — some builders and security plugins do. Reopen the page in the editor and check the code is still there.
• It works in the editor but not on the live site, or the reverse. Squarespace in particular shows a placeholder while editing. Always judge from the published page in a normal browser tab.
• A short box with a scrollbar. The widget did load. Wix especially needs the element given a generous height on the canvas; it will not always grow to fit.
• The snippet was retyped or edited. Paste a fresh copy from Settings → Branding & embed rather than repairing it by hand.

If there is still nothing

Open the Direct link from the same screen in a new tab. That separates the two possibilities cleanly:

• The link works, the embed does not — the problem is on your website, in how the code was pasted.
• The link does not work either — the problem is the venue, not the website. Almost certainly it is not live.

And if your site simply will not allow custom code, put the direct link on a button. It works everywhere and costs only the guest leaving your page.