Passing values dynamically to a text field

I previously built a WP site with a CF7 form where I was able to dynamically pass a value to one of the text fields by using the instructions at https://contactform7.com/getting-default-values-from-the-context/
The contact form has this shortcode:
[text* room default:get]
and it works perfectly, as you can see here:
https://www.balmashanner.com/room-enquiry/?room=The+Lour+Kingsize+Room
I followed the same exact process on a new site, where the shortcode is as follows:
[text* product default:get]
But this time for some strange reason the dynamic links aren’t working and I get a 404 error:
https://www.dev.epackmachinery.co.uk/product-enquiry/?product=Test
I can’t for the life of me understand what’s different, unless it’s the new version of CF7 that no longer works the same way. If so, what is the correct way?

The page I need help with: [log in to see the link]