As detailed in How does the ajax search work ?, wpsolr will try to replace your theme’s search boxes with its own.
But, if your theme does not use the standard WordPress “get_search_form” filter to build its search boxes, nothing will happen.
A way to overcome that issue is to insert a link to the ajax search page “search-wpsolr” in your pages.
Or you can show the standard search widget on your pages, it will be replaced automatically.
Or you can include the standard search box in your theme template(s), with:
<?php echo get_search_page(); ?>