HTML code not working - direct copy between two Squarespace sites

Hi, I have some custom html code that works as shown here: www.highnorth.co.uk/critical-power-calculator.  Essentially, a user inputs a few values, and then there is some JS code that calculates outputs automatically. 

I have directly copied the code onto a second website I have. Both are Squarespace version 7.1.  However, the code is not working properly. The form renders correctly on the second website (i.e. the form looks correct). The user can also input values. However, the outputs aren't generating automatically. I can't figure out why. It seems as though the JS code isn't working properly, or something is blocking the page from generating the outputs. 

Does anyone have any ideas what might be happening. I looked into switching AJAX loading off, which I read can interfere with the code, but I don't think that's an option in version 7.1. 

Thanks!

Just to add also, that the page on the original site (the one that's working) was made under Squarespace 7.0, before the whole site got upgraded to 7.1. So I think it's maybe something to do with the change of versions?

Do you have link to second site? We can check problem easier