Hi Pamella
I just had a look, thanks for the vid…
That tick box will absolutely not make/break anything, and you can disable it no problem.
It seems as if something is breaking the JS on the page, or maybe there is a hidden error.
Have you tried creating a new search form?
Sometimes other plugins can affect S&F (such as your listly plugin) by placing elements on the S&F page and potentially breaking it.
Try creating a new search form and let me know if the problem still occurs? If it does then I would suggest that there is another change in your site that has caused this problem (such as another plugin) – I think it was complete coincidence that when you checked this box the form broke.
Thanks