Hi!
It’s very hard to tell without further information. First you should try to go through the steps in this knowledgebase article: https://wp-dreams.com/knowledge-base/when-i-type-in-something-the-search-wheel-is-spinning-but-nothing-happens-why/
These issues are rare, and are mostly related to a 3rd party plugin or a theme (mostly duplicate function names or similar). If you can link me to a page where the search is active, I can check the ajax response, maybe it throws some kind of error message that I can examine. In this case temporary administrator and ftp access would be great, so I can do further debugging to find the source of the issue. You can safely provide those by editing your first post and filling out the desired fields.