code block not allowing Javascript / iframe embeds even after upgrading to the relevant plan

Squarespace is not officially here. Please see item seven on the forum guidelines. This forum is provided by SS to it's users as a way for forum members to help each other. There is only one official way to Contact Customer Support.

The business plan or above allows JavaScript or iframes to be run.

It doesn't guarantee the code you install will work. JavaScript and iframes involve running computer code. In addition iframes also can involve security permissions. If the source for the iframe code denies you access then that has nothing to do with the business plan or Squarespace.

It is much like buying a car. Buying the car doesn't guarantee you will be able to get from point a to b, if the car was broken down when you bought it. There is potential but no guarantee.

A side note. SS often allows JavaScript and iframes to work without the business plan while in the editor for testing purposes. So you can test out code before going live. It's just that the code won't work for the outside world unless you get the business plan or above.

Please post the URL for a page on your site where we can see your issue and describe what the code is supposed to be doing and where on the page it should be.

A link to the backend of the your site won’t work for us, i.e. a url that contains /config/.

Please set up a site-wide password, if your site is not public and you've not already done so.

Post the password here.

Adding a site-wide password does not allow anyone to alter your site. It only allows those with the password to see your site.

Please read the site-wide password and how to share a link documentation to understand how they work.

We can then take a look at your issue.

You may find How to post a forum question post useful.