In order to create a Deckbuilder page on your website, you will need to add or update a Deckbuilder site page under your Design tab.

Go to Design > Site Pages and create a new site page with the blue cross button on the right:

On the new site page, provide a title 'Deckbuilder' which will be how it gets displayed on your website.

The SEO Name must be:
​products/multi_search

Keywords and Description are optional.

For the Tags section, you must add either nav-main (to make the Deckbuilder appear at the top) or nav-footer (to make the Deckbuilder appear at the bottom).

Finally his Save Page.  You may need to run a /?force=true on your store website to refresh the cache, but you will have the deckbuilder now.