Introducing a new change in website caused reduced traffic

On our website, we introduced new changes as the following scenario:

Before: Enter zip code in Homepage ---> locations page

Now: Enter zip code in Homepage ---> shop page

Now, SEO has mentioned that visitors reaching shop pages after zip-in has dropped.

Wondering what the reason could be. Every time I test the zip-in functionality, it works fine and takes to the shop page as expected (no errors).

Any insights or suggestions from an SEO perspective would be highly appreciated. Thank you!