I could confirm the issue on your shared site.

Please try resetting the search form on your site on clicking on the Reset button of search form.

This can be due to plugin conflict on your site so please try temporary deactivating all plugins except Ivory Search plugin and see whether everything works fine and then enable the plugins one by one to see which plugin is conflicting if any.

Would you mind if I log in to your site and do some troubleshooting? If this is ok then could you please share me your site log in details privately by checking the option “Set as private reply” when replying to this topic?

I hope you are well today and thank you for your question.

It depends on how you have configured the search form settings so please make sure you have configured it correctly referring the information provided in the below page.

Documentation

Also, please try resetting the search form by clicking on the Reset button and then configure the search form.

If it still doesn’t work then could you please share me the screenshots of the search form settings that you have configured?

Would you mind if I log in to your site and do some troubleshooting? If this is ok then could you please share me your site log in details privately by checking the option “Set as private reply” when replying to this topic?

Best regards,
Ivory Search Support

You can achieve this by removing the above shared CSS code and using below CSS code.

#mega-menu-wrap-main-nav .is-menu input.search-field {
    float: left;
    margin: 0;
}

#mega-menu-wrap-main-nav .is-menu .search-submit {
    padding: 11px 10px;
    min-width: 0;
    font-size: 14px;
    float: left;
    height: auto;
    line-height: 14px;
    margin: 0;
}

#mega-menu-wrap-main-nav .is-menu  .search-close {
    top: 38px;
    right: 8px;
}

Yes, the Ivory Search plugin needs to enable as without enabling it I can’t see the search form on your site.

After enabling it, you can just hide it for your site users so that it won’t display broken by adding the below CSS code in the Custom CSS option of Ivory Search plugin settings on the path Ivory Search -> Settings -> Settings

.is-menu {
display: none !important;
}

I hope you are well today and thank you for your question.

We can certainly make it work.

Are you using same plugins on all of your 3 sites?

Does the default WordPress search form work fine on that site?

Could you please share me the page URL from your site where the search form is displaying so that I can troubleshoot it?

Best regards,
Ivory Search Support