Recent answers to When I open Firefox, the top of the browser isn't there.https://support.mozilla.org/ar/questions/12736152019-11-24T08:04:44-08:00Try to rename/remove xulstore.json in the Firefox profile folder with Firefox closed.
You can use th2019-11-24T08:04:44-08:00cor-elhttps://support.mozilla.org/ar/questions/1273615#answer-1268738<p>Try to rename/remove <b>xulstore.json</b> in the Firefox profile folder with Firefox closed.
</p><p>You can use the button on the "Help -&gt; Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:profiles</b> page.
</p>
<ul><li>Help -&gt; Troubleshooting Information -&gt; Profile Directory/Folder:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
</li><li><a href="https://support.mozilla.org/en-US/kb/Profiles" rel="nofollow">https://support.mozilla.org/en-US/kb/Profiles</a>
</li></ul>