Hello, at first you can try to clear cache.
Then, you can see, what you have in this file, where the code is: themes\classic\templates\_partials\helpers.tpl
In classic theme it looks like:
{function renderLogo}
<a href="{$urls.pages.index}">
<img
class="logo img-fluid"
src="{$shop.logo_details.src}"
alt="{$shop.name}"
width="{$shop.logo_details.width}"
height="{$shop.logo_details.height}">
</a>
{/function}
Also, you can see this file: \themes\classic\templates\_partials\header.tpl
You need to take note to such code here:
<div class="col-md-2 hidden-sm-down" id="_desktop_logo">
{if $shop.logo_details}
{if $page.page_name == 'index'}
<h1>
{renderLogo}
</h1>
{else}
{renderLogo}
{/if}
{/if}
</div>
if Everything is ok, above, then the problem is in the database data. See what you have in Traffic & SEO tab in BackOffice.