Remove category from query (show all posts in archive.php) pre_get_posts()

Just unsetting the cat variable probably isn’t enough. The pre_get_posts hook happens after the query variables have already been parsed. So there’s probably a tax_query with the taxonomy = category and the terms = your category.

You’re already dumping the $query in your code, presumably for debugging. So, look at what you’re actually dumping. Do you see the tax_query? Change your code to adjust that $query to have what you want it to have.