Using a simple language drop-down to switch languages

<li>
            <a href="" class="no-link" data-bs-toggle="dropdown-menu-lang" title="languages">
                <span itemprop="name">{phrase:working_language}</span>
            </a>
            <ul class="submenu">
            {exp:publisher:languages}
                <li menuitem itemscope itemtype="http://schema.org/SiteNavigationElement">
                    <a itemprop="url" href="{switch_language_url}">{long_name}</a>
                </li>
            {/exp:publisher:languages}
            </ul>
<p>        </p>
</li>

Works perfectly on every page we’ve tested it on *except* the home page - which does not appear to be affected by choice (site continues to show default language).
We’ve looked for settings and in docs but so far not found anything that might be the cause.
Any thoughts / ideas would be most valued.